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Training CourseHandouts
Course held byJotun Marine Coatings
Sandefjord10 -11 January 2001
PaintSchool
Jotun Paint School Course Handouts Page 1
Jotun Paint School
Course Handouts
Contents
Chapter Title Page
1 Introduction 2
2 What is Paint? 3
3 Generic Paint Types 8
4 Steelwork 15
5 Pre-treatment 19
6 Paint Application 26
7 Inspection and Control 33
8 Paint Failures 41
9 Antifouling 47
10 Safety, Health and Environment (SHE) 53
11 Corrosion 59
12 Cathodic Protection 65
Jotun Paint School Course Handouts Page 2
1. Introduction
Why paint?There are two main reasons for painting. For many people, the most important reason is thatwe want pleasant surroundings (decorative painting). In other contexts, paints are appliedbecause it is financially very important to protect structures against corrosion. For thesepurposes, corrosion-protective paints are used. A good paint system will be a cost-effectivemethod of protecting the structure: The life of the structure is extended, maintenance costs arereduced and the risk of accidents which affect people and the environment is reduced.
Painting and cathodic protectionFor most applications, painting has been found to be the simplest and most economical way ofprotecting structures, regardless of the exposure environment and your location in the world.
When a structure requires protection, it is important to select a paint system suitable for thepurpose. Paint is a semi-finished product and the protection will be no better than the qualityof the finished coating. The human factor applies during both pre-treatment and application. Apaint system is also often exposed to mechanical wear, which can cause weakness/damage tothe paint film. Where damage occurs, the substrate (normally steel) begins to rust. Jotun hastherefore developed a concept called the "Single Source Solution". This concept enables us toprovide cathodic protection as a back up for corrosion-protective paints. The aim is to ensureoptimum cost solutions for protecting structures exposed to water. Cathodic protectionprotects damaged areas in the paint film.
JotunJotun is one of the world's leading suppliers of corrosion-protective paints for industry,shipping and oil-related sectors. We also supply paints for decorative purposes and powderproducts, based on a worldwide network of factories and companies. To support customers,we have established a wide range of services. This ensures that the customer receives the rightpaint products from our corrosion-inhibiting systems at optimum cost.
Jotun Paint SchoolAs part of our service, Jotun arranges paint courses. These can be courses of more generalcharacter or specific customer-related courses. They focus on the practical use of paint. Tofind out more about these courses, contact your local Jotun office for more information.
Course HandoutsThe course handouts contain a brief introduction to the main topics of paint technology. Eachsection consists of an introductory section and a copy of selected overhead slides. Not alltopics in the handout will necessarily be discussed on the course you follow.
Welcome to the Jotun Paint School !
Jotun Paint School Course Handouts Page 3
2. What is Paint ?
Definition of paint and varnish
Paint is a product in liquid or powder form which contains pigments and which is applied to asubstrate to form an opaque film. The film has protective and/or decorative properties and canalso be given special functions as required. Paint is described as opaque if it hides thesubstrate completely.
Varnish is a product which, when applied to a substrate, gives a solid transparent film andhas protective, decorative or special properties. Varnish does not contain covering pigmentsand is therefore regarded as "clear paint".
What is paint made of?
The main constituents of paint are binder, pigment, extender (filler), solvent and additives(auxiliary substances).
The binder is the most important component of paint. The binder gives the paint most of itsproperties such as adhesion to the substrate, resistance to weathering, water, chemicals,temperature etc. Binders can be divided into groups (generic types) depending on the dryingor curing process which takes place after the paint has been applied to the substrate. The firstgroup are known as oxidatively drying, as the paint absorbs oxygen from the air and dries.Example: alkyd paints. The next group are called physically drying. When the paint is appliedto the substrate, the solvent simply evaporates. Examples: chlorinated rubber and acrylic. Thethird and final group contains chemically curing paints. These paints are usually two-component, e.g. epoxy.
Pigments in a paint can be colour pigments which give the paint opaqueness, the desiredshade etc. Colour pigments, both organic and inorganic, are available in many shades.Titanium dioxide is a strong colouring, white pigment with good opaqueness and is used inwhite and pale colours. Rust-inhibiting pigments include zinc (cathodic protection) and zincphosphate (inhibiting protection). Such pigments are used only in primers (first coat).
Extenders or fillers such as dolomite, talcum etc. have little or no opaqueness and aretransparent in the binder. They have different forms e.g. balls, needles, fibres etc. and are usedto give a sealed film, the right gloss etc. In antifouling paints, for example, copper oxide isused as a pigment to prevent fouling of ships’ hulls.
Solvents are added to the paint to adjust the viscosity so the paint can be applied by brush,roller or spray gun. Different binders require special solvents or solvent mixtures to be able todry or cure in such a way that the paint properties are not damaged.
Additives are a small, but important, part of the paint. Such substances include antisettlingagents (to prevent fouling), thickeners (to prevent sagging / running), antifoaming agents (toprevent air entrapment), etc.
Jotun Paint School Course Handouts Page 4
How does paint protect the substrate ?
Paint protects the substrate in three main ways: barrier effect, inhibitor effect and galvaniceffect. Paints which have a barrier effect only form a barrier between the substrate and theenvironment and no rust-inhibiting pigments are added. Most paints come under this group:many primers, all intermediate coats and top coats. Aluminium and glass flakes are often usedin primers to increase the barrier effect.
Paints which use the inhibitor effect contain inhibiting pigments e.g. zinc phosphate. Suchpigments are only used in primers. Paints in this group are not suitable for use under water.
Paints with a galvanic effect contain pure zinc pigments and are used only as primers. Thebasic principle is that the zinc makes metallic contact with the steel so that the zinc can act asan anode. If the paint system is damaged, the zinc pigments will protect the exposed steelcathodically (see section on Cathodic Protection).
What does a paint system consist of?
In most cases, a paint system consists of 2 to 4 coats and is built up from a primer coat, one ortwo intermediate coats and a top coat. The three main constituents in the paint system can bethree different paints, but it is not unusual to use a particular paint as both primer andintermediate coat. Each part of the system has a specific function and it is therefore importantto follow the instructions of the paint manufacturer and the recommended system structure toachieve the best possible result. The main purpose of primers is to ensure good adhesion ofthe system to the substrate. Intermediate coats usually ensure that the system is sufficientlythick to create a good barrier from the surrounding environment. The top coat gives thesurface the right colour, a good durable gloss and protection against the external environment.
A paint system can include more coats than stated above. In brief:
• Shop primer, primarily for the temporary protection of steel from production through tothe construction stage.
• Tie coat, which is applied to porous surfaces to prevent pinholes or to ensure goodadhesion between coats (tie coat).
• Mid coat. More than two are used for paints which cannot be applied in thick coats.
Personal notes
Chapter: What is Paint ?
Jotun Paint school Handouts Page 5
Paint School1
Paint consist of:Paint consist of:
•Binder•Colour pigments•Extenders•Solvents•Additives
Paint School2
The properties of a paint will beThe properties of a paint will bedecided by the binderdecided by the binder
• Describes the type ofpaint/coating
• Bind pigments andextenders to a solid film
• Provides the adhesion tothe substrate
• Provides the water, chemical,solvent and UV resistance
Paint School3
Oxidising• Alkyd
Physically drying• Chlorinated rubber• Vinyl• Acrylic• Asphalt• Tar
Chemically curing• Epoxy• Polyurethane• Polyester• Silicate
Curing mechanism of bindersCuring mechanism of binders
Paint School4
Oxygen enter.Reaction starts:
Polymer molecules linked together through chemical bonds
Curing (drying) through oxidationCuring (drying) through oxidation
Solvents evaporating
Paint School5
Solvents evaporating
Polymer molecules stick together (no chemical bonds):
Physical drying.Physical drying.Solvent borne paintsSolvent borne paints
Polymer molecules are packing:
Paint School6
Physical dryingPhysical dryingWaterborne paintsWaterborne paints
= Dispersed droplets
Water evaporating
Droplets are packing
Droplets melt together, co-solvents evaporate
Chapter: What is Paint ?
Jotun Paint school Handouts Page 6
Paint School7
= Polymer = Curing agent (hardener)
Solvents evaporating
Curing mechanism of Curing mechanism of two -pack paintstwo -pack paints
Polymer & hardener molecules reacted to form a new chemical substance:
Paint School8
VinylChlorinated rubberEpoxyPolyurethane
Urethane alkydAlkydBoiled linseed oilRaw linseed oil
The surface tolerance depends on the The surface tolerance depends on the penetrating properties of the binderpenetrating properties of the binder
Surface tolerant paint:Epoxy Mastic
Paint School9
Rust preventing pigments:• Red Lead• Zinc• Zinc Chromate• Zinc phosphate
Extender pigments (non/limited hiding/opacity properties):• Talcum• Barium sulphate• Microdol (dolomite)
Pigments, examplesPigments, examples
Coloured pigments (hiding power / opacity):• Inorganic; red, yellow, brown, black• Organic, all colours• Titan dioxide (white)
Paint School10
The Gloss of a paint depends on the PVCThe Gloss of a paint depends on the PVC(Pigment - Volume - Concentration)(Pigment - Volume - Concentration)
Colour pigments
Binder
Extenders
SemiglossPVC 30 - 40
FlatPVC 35 - 50
GlossyPVC 15 -25
Paint School11
• Dissolve the binder• Give lower viscosity• Give application properties
for brush, roller, spray
Solvents / Solvents / diluentsdiluents
Paint School12
Solvent or Solvent or diluentdiluent
• Single or blended• Disolves the binder completely
(Forms a solution)
• Single or blended• Does not dissolve the binder (Forms a “mixture”)• Used in conjunction with solvents
DiluentDiluent
SolventSolvent
Chapter: What is Paint ?
Jotun Paint school Handouts Page 7
Paint School13
Addition of thinnerAddition of thinner
Evaporation rate and solubility of athinner will influence a paint’s:
• Drying time• Film-forming properties• Quality of the film
❶ Most paints are ready to be applied as supplied by the manufacturer.❷ Never add an unspecified thinner to a paint, it may lead to disastrous results
Paint School14
• Wetting agent• Anti-foam• Anti-settling• Anti-skin• Anti sagging• Catalysts• UV-absorbers etc.
AdditivesAdditives
Paint School15
Corrosion protection by paintsCorrosion protection by paints
• Barrier effect• Inhibitor effect• Galvanic effect
For corrosion prevention with paints, three mainprinciples are employed:
Paint School16
PrimerSteel
1st coat2nd coat
Impervious to ions,oxygen, carbon dioxide
Low moisture transmission
Strong adheringcoating thoroughly wets steel surface Physical as well as
chemical adhesion
No voids at interfaceto accumulate water
Clean surface - no saltsto create osmotic blistering
An impervious coating serves as an An impervious coating serves as an inert barrier to protect the surface inert barrier to protect the surface
Paint School17
Moisture may penetrate to reach the inhibitiveprimer where the reactive pigments are activated, which in turn
passivate the metal substrate at the coating/metal interface.
InhibitionInhibition
Inhibitive Primer1st Coat2nd Coat
Steel
Moisture Absorption
Ionisation of InhibitorReaction with Steel Surface
Passive layer forms
Paint School18
Inorganic Zinc Primer
2nd Organic Topcoat
Superior adhesion prevents coating undercut
Moisture allows Zinc toionize, cathodically protecting the steel.
Damage in coating to steel surface
An inorganic Zinc primer reacts to protect thesteel substrate when the topcoat is damaged.
Cathodically protective pigments Cathodically protective pigments
SteelZn2+
Jotun Paint School Course Handouts Page 8
3. Generic Paint TypesIt is not possible to develop a "universal" paint which fulfils all possible functions. Paints aretherefore developed for different jobs. As a result, each paint has a different set of properties.Paints are often grouped according to the chemical composition of the binder, which we referto as ‘generic paint types’. To ensure that you choose the right paint or paint system with theright properties, it is important to know the strengths and weaknesses of the various generictypes.
Alkyd paints
Alkyd paints are made from alcohol and acid with the addition of fatty acid or oil. Theaddition of fatty acid and/or oil can be varied to give alkyds with different properties.
Alkyd paints can only be used above water (not submerged) as the water resistance is poor.They are not used on zinc primer or galvanised steel as a chemical reaction - saponification -would occur with the binder, with subsequent blistering and flaking. The drying/curingprocess is also temperature-dependent. This is because alkyd paints dry or cure by absorbingoxygen from the air. This is a chemical reaction and such reactions are always influenced bytemperature.
The degree of pre-treatment required for the substrate can vary from St 2 to Sa 2½, dependingon the purpose of the paint and the environment to which the paint is exposed. By modifyingthe alkyds for example with styrene or silicon, other properties can be achieved.
Physically drying paints
The group of physically drying paints contains generic types such as chlorinated rubber (CR),vinyl and acrylic-based paints. These are being withdrawn from the market due to the highcontent of volatile organic compounds (VOC). The chlorinated compounds in CR paints alsogive off chlorine on ageing.
Physically drying paints are single-component, and dry by pure evaporation of the solvents.This means that these paints are not so sensitive to the ambient temperature during applicationand drying (does not apply to waterborne acrylic). They are also resoluble by other paintswhich contain strong solvents or in contact with thinners.
CR paints are used outdoors both above and under water. Vinyl-based paints are used onlyabove water. Acrylic is used as a top coat, as it retains its gloss better than chlorinated rubberor vinyl in such systems. acrylic is also used as primers in waterborne systems.
Chemically curing paints
Chemically curing paints are thermosetting plastics, unlike physically drying paints which arethermoplastics. Thermosetting plastics are more resistant to chemicals than thermoplastics asthey form an insoluble three-dimensional network after curing.
Jotun Paint School Course Handouts Page 9
These paints are normally two-component. The supplier provides these paints in two separatecontainers, one for the base and the other for the curing agent. We often refer to these ascomponent A and component B. Before painting, the two components must be mixed. It isparticularly important to mix the components in the correct ratio and to ensure good agitation.The curing process is a chemical reaction between the base and curing agent, so applicationand curing are temperature-dependent. It is equally important to apply the paint to thesubstrate before the chemical reaction has proceeded for too long after mixing of thecomponents. We often talk of the usage time (potlife) of paints. When the potlife has elapsed,the paint becomes dry and finally completely hard and cannot be applied.
Some chemically curing paint types
Epoxy paints have excellent chemical resistance, particularly to alkalis. They have goodadhesion both to steel and concrete and good water resistance. Epoxy can be modified usingphenol, coal tar and hydrocarbon resin to give special properties, e.g. better chemicalresistance, better penetration, better water resistance etc. One drawback with many epoxypaints is that they contain large quantities of solvent. However, other types have now beendeveloped with a high solids content (mastic products) with excellent "all round" properties.There are also a solvent-free epoxy paints which are used for drinking water tanks.Waterborne Epoxy paints are increasingly being used today because they give a betterworking environment. Chemical resistance however is slightly reduced.
Zinc epoxy (organic) or zinc ethylsilicate (inorganic) are used as cathodic protective primerson blast-cleaned substrates. Zinc ethylsilicate (solvent-based) and alkali silicate (waterborne)are also often used inside storage tanks for solvents because of the extremely good solventresistance.
Polyurethane paints are also thermosetting plastics. They are used as top coats on epoxy(which chalks in sunlight) as they have excellent weather-resistance and durable gloss.
Polyester paints are thick coat paints used in areas where a high degree of wear resistance isrequired. For example gangways, production decks, dam walls (concrete) for power stationsetc. These paints are applied in thick coats (e.g. 2 x 750 µm) and cure quickly (a few hours).They also have good chemical resistance.
Vinylester is also a thick coat paint (2 x 750µm). It has good chemical resistance and is oftenused inside storage tanks for chemicals. Such paints can be used on both steel and concrete.
Personal notes
Chapter: Generic types
Jotun Paint school Handouts Page 10
Paint School1
• Good applicationproperties
• 1-component• Good weather durability• Good wetting properties• Good recoatability• Good levelling properties• Good gloss retention• Dry heat resistant up to
120 ºC.
• Poor chemical resistance(especially againstalkaline)
• Limited water resistance(submerged)
• Limited solvent resistance• Limited film thickness per
coat• Poor adhesion to CR• Never to be used on Zinc
Alkyd paintsAlkyd paintsPropertiesProperties
Advantages Limitations
Paint School2
• Ships• Industry
• Newbuildings / Maintenance• All exterior and interior objects• Only above water
• St 2 to Sa 2½ or shop primedsteel
Segments
Objects
Surface preparation
Alkyd paintAlkyd paintWhere to useWhere to use
Paint School3
Advantages• Physically drying• Not temperature
dependent• Easy to recoat• One component• Very good water
resistance• Relatively good chemical
resistance
Limitations• Poor solvent resistance• Low solid content• Relatively poor wetting
properties• Thermoplastic• Dry heat resistant up to
approx. 70 °C
Chlorinated Rubber paintsChlorinated Rubber paintsPropertiesProperties
Paint School4
Chlorinated Rubber paintsChlorinated Rubber paintsWhere to useWhere to use
• Ships• Offshore• Industry
• Newbuildings / Maintenance• Below and above water• All external surfaces
• Blast-cleaned to Sa 2½ or shopprimed steel
Segments
Objects
Surface preparation
Paint School5
Advantages Limitations• Low solid content • Poor resistance against strong solvents• Dry heat resistant up to approximately 80 ºC
Used for:
Vinyl paintsVinyl paintsPropertiesProperties
• Physically drying • Good chemical resistance• Good water resistance• Quick drying• Not temperature dependent• One-component
Exterior objects above water Offshore on top of Zinc-ethylsilicate
Paint School6
Advantages• Higher content of
solids• Higher water
resistance• Better wetting
properties• Cost advantages
Disadvantages• Bleeding• Dark colours• Tar on cancer list
Used for: Under water areas
Vinyl Tar - Modified typeVinyl Tar - Modified typePropertiesProperties
Chapter: Generic types
Jotun Paint school Handouts Page 11
Paint School7
Advantages
• Chemical curing• Very good chemical resistance• High alkali resistance• Moderate resistance to acids• Good adhesion• Very low permeability• High mechanical strength• Dry heat resistant up to 120 °C
Limitations
• Chalking• Temperature dependent• 2 - component• Requires blast cleaning• Overcoating time
Pure Epoxy paintsPure Epoxy paintsPropertiesProperties
Paint School8
Pure Epoxy paintsPure Epoxy paintsWhere to useWhere to use
• Ships• Offshore• Industry
• Newbuildings / Maintenance• Chemical cargo tanks
• Blast-cleaned to Sa 2½ or shop primed steel
Segments
Objects
Surface preparation
Paint School9
Advantages:• Chemically curing • More flexible
• Excellent water resistance
• Better wetting properties
• Dry heat resistant up to 90 °C
Limitations:• Dark colour
• Temp. dependent
• 2-component
• Recoating interval
• Bleeding when overcoated
• Coal Tar is carcinogenic
Epoxy Coal TarEpoxy Coal TarPropertiesProperties
Paint School10
Epoksy - acrylicEpoksy - acrylicPropertiesProperties
• Very good weatherresistance
• Very good gloss retention• Very good chemical
resistance• Very good solvent
resistance• Cures down to 0 °C• Potlife (24 timer)
• 2-pack• Overcoating time
Positive Limitations
Paint School11
Epoksy - acrylic pintsEpoksy - acrylic pintsWhere to useWhere to use
• Ships• Offshore• Industry
• Newbuildings / Maintenance• Above water• Indoor and outdoor
• Top coat on Epoxy, Epoxy• Mastic, Polyester glass flake
Segments
Objects
Surface preparation
Paint School12
Advantages• Chemically curing • Surface tolerant • Light colours• Very good water resistance • Very good wetting properties • Good chemical resistance• High solid content• High build (Thick coats) • Winter curing agent• Dry heat resistant up to 90 ° C
Limitations
Epoxy Mastic paintsEpoxy Mastic paintsPropertiesProperties
• Chalking• Temperature dependent• Not to be applied on thick coats of physically drying paints• Minimum DFT 150 µm by airless spray
Chapter: Generic types
Jotun Paint school Handouts Page 12
Paint School13
Epoxy Mastic paintsEpoxy Mastic paintsWhere to useWhere to use
• Ships• Offshore• Industry
• Newbuildings / Maintenance• Ballast tanks and Cargo tanks• All exterior and interior surfaces,
above and below water• St 2 to Sa 2½ or Water jetted,
Magnesium descaled or shopprimed steel
Segments
Objects
Surface preparation
Paint School14
• Correct mixing ratio• Good mixing• Potlife• Induction time• Correct pre-treatment• Correct film thickness• Adequate ventilation
• Temperaturedependent curing
• Avoid high humidity• Minimum and
maximum curingtimes
• Time for fully cured• Use epoxy thinner• Health and epoxy
ExperienceExperienceWhen using Epoxy paintsWhen using Epoxy paints
Paint School15
• Very good weatherresistance
• Excellent glossdurability
• Very good chemicalresistance
• Very good solventresistance
• Cures down to 0 °C
• 2-pack• May cause skin
irritation• Overcoating time
Polyurethane paintsPolyurethane paintsPropertiesProperties
Advantages Limitations
Paint School16
Polyurethane paintsPolyurethane paintsWhere to useWhere to use
• Ships• Offshore• Industry
• Newbuildings / Maintenance• All exterior substrates above
water (Also internal at times)• On top of Epoxy, Epoxy Mastic
and Polyester coatings
Segments
Objects
Surface preparation
Paint School17
Zinc EpoxyZinc EpoxyPropertiesProperties
• Chemically curing• Good corrosion protection• Good adhesion• Require min. Sa 2 ½• Good mechanical strength• May be recoated with all
types of paint, except Alkyd• Dry heat resistant up to 120
ºC
• Temperature dependent• 2-component• Film thickness: 25 - 50 µm• Not acid- and alkaline
resistant(Resistant between pH 5-9)
Advantages Limitations
Paint School18
Zinc Epoxy paintsZinc Epoxy paintsWhere to useWhere to use
• Ships• Offshore• Industry
• Newbuildings / Maintenance• All exterior and interior objects
above and below water (as holdingprimer for underwater use 20-30microns).
• Blast-cleaning to minimum Sa 2½
Segments
Objects
Surface preparation
Chapter: Generic types
Jotun Paint school Handouts Page 13
Paint School19
Zinc Zinc EthylsilicateEthylsilicate paints paintsPropertiesProperties
• Very good solvent resistance• Very high heath resistance
(max 400 oC)• Very high mechanical
strength• Very good adhesion to blast
cleaned steel• Relatively good re-
coatability
• Requires humidity forcuring
• 2-pack• Max. DFT: 100 µm
At higher DFT tendencyof mud-cracking orchecking
Advantages Limitations
Paint School20
Zinc Zinc EthylsilicateEthylsilicate paints paintsWhere to useWhere to use
• Ships• Offshore• Industry
• Newbuildings / Maintenance• All exterior objects above the
waterline.• Tank coating and Water ballast tank
(No paint on top)• Blast-cleaning to minimum Sa 2½
Segments
Objects
Surface preparation
Paint School21
Aluminium Silicone paintsAluminium Silicone paintsPropertiesProperties
• Pure aluminium silicone:Resistant up to approximately 600°C
• Modified aluminium silicone:Resistant up to approximately 400°C
• To be applied in thin coats only (20 µm)Heavier coats may give blistering
Remember:To be applied on Sa 2 ½Overcoating only on fully cured Zinc silicate
Paint School22
Waterborne acrylicsWaterborne acrylicsAdvantages andAdvantages and LimitationsLimitations
• Good corrosion protection• Reduce the emission of
solvents• Low VOC content• Flash point above 100 ºC• Water as thinner / cleaner• Good water resistance• Good UV - resistance• Good adhesion to other
generic type of paints• No risk of saponification
• Due to water-solublegroups, more sensitive toaqueous solutions (moreblistering/earliercorrosion)
• Slower drying comparedto solvent based types athigh relative humidity
• Need good ventilation• Need good pre-treatment• Less chemical resistance
Advantages Limitations
Paint School23
Waterborne epoxyWaterborne epoxyAdvantages and limitationsAdvantages and limitations
• Good corrosion protection• Reduced emission of solvents• Low VOC content• Flash point above 100 ºC• Water as thinner / cleaner• Good water resistance• Cures down to 5 ºC• Good adhesion to steel,
galvanized steel, Aluminiumand concrete
• Good sprayability
• Need good ventilation at highhumidity
• Must be stored above 0 ºC• Shorter potlife compared with
solvent borne• The same health hazards as
solvent borne Epoxies• Due to water-soluble groups,
more sensitive to aqueoussolutions
Advantages Limitations
Paint School24
Recommended conditionsduring application and drying
Application and drying possible
Application not recommended
10 20 30 40 50 60102030405060708090
100
Temperature ( oC)
Relative humidity (%)
Waterborne paintsWaterborne paintsConditions during applicationConditions during application
Chapter: Generic types
Jotun Paint school Handouts Page 14
Paint School25
GlassflakeGlassflake Reinforced Polyester Reinforced Polyester
• For protection of steel and, in certain cases,Aluminium and concrete.
• The glass-flakes are 3-5 microns thick and400 microns across.
• Potlife : Approximately 45 minutes.• Curing time: Approximately 3 hours.• Thickness 600 - 1500 microns per coat.
Paint School26
GlassflakeGlassflake Reinforced Polyester Reinforced PolyesterPropertiesProperties
Advantages• Quick curing• Variable curing time• Application with airless• Excellent mechanical strength
• Glass-flakes reduce shrinkage,increases mechanical strengthand water resistance.
• Very good chemicalresistance
Limitations• Temperature dependent• Short potlife• Recoating interval
2 - 12 hours
• Bad curing may beexperienced on Zinc primersand galvanised surfaces.
Paint School27
GlassflakeGlassflake Reinforced Polyester (Styrene free) Reinforced Polyester (Styrene free)PropertiesProperties
Advantages• Styrene free• Dry to handle in 2 hours• Cures down to 5 ºC (2-component pump)• Excellent mechanical
strength
• Very good adhesion
• Very good water resistance.
• Very good chemicalresistance
Limitations• Cures down to 10 ºC
(normal airless spray)• Short potlife• Recoating interval
1 hour to 2 weeks (23 ºC )• Require Sa 2 ½ and a roughness
of 50-100 microns
• Bad curing may be experiencedon Zinc primers and galvanisedsurfaces.
Paint School28
Vinyl ester coatingsVinyl ester coatings
Glass-flake reinforced Vinylester coatingfor protection of steel and concrete
in aggressive environments.
Paint School29
Vinyl ester coatingsVinyl ester coatingsAdvantages and limitationsAdvantages and limitations
• Very fast curing• Very good adhesion• Very good abrasion
resistance• Very good chemical
resistance• Very good solvent resistance• Can be applied by normal
airless spray• Glassflakes improve abrasion
resistance
• Very fast curing• Very good adhesion• Very good abrasion
resistance• Very good chemical
resistance• Very good solvent resistance• Can be applied by normal
airless spray
Advantages Limitations
Paint School30
Application ofApplication ofPolyester and Vinyl ester coatingsPolyester and Vinyl ester coatings
• Capacity of pump, min.12 l/min (airless)
• Material hose: 3/8”• Use teflon gaskets• Nozzle: 0,035-0,053
Angle 40 - 80 o
• Remove filters• Check the W.F.T.
• Check ventilation, light etc.• Thinner No. 17 or 15,
Acetone for flushing orcleaning
• Only on blast-cleaned steel• Proper mixing• Short potlife
Jotun Paint School Course Handouts Page 15
4. SteelworkBefore a structure is painted, a number of operations must be performed on the substrate. Theinitial work required is generally known as "steelwork". Steelwork is a very important part ofthe surface treatment and must be carried out before cleaning and priming of the steel. Goodsteelwork will ensure that the life time of the paint system meets expectations. In practice, it isimpossible to achieve a long life time for a paint system if the steelwork is omitted or poorlyperformed. The requirements for preparation will always be part of the paint specification.
A steel structure should be designed so that all parts of the structure are accessible forcleaning, pre-treatment and painting. It is particularly important to ensure that theserequirements are taken into account at the newbuilding / construction stage. Designers oftenforget that structures require maintenance.
Steelwork involves the following stages before cleaning and priming:
1. All sharp edges are rounded to a radius of at least 2 mm by grinding.2. All welding beads and slag are grinded off.3. Surface defects such as lamination etc. are removed by grinding.4. Undercutting in the weld is repaired before priming.5. Rough manual welds to be grinded.6. Gas-cut edges are to be grinded before priming.
To avoid contamination and damage to the coating, steelwork should be performed in thewelding shop and not in the paintshop. Production times will also be reduced if sharp edges innotches, manholes etc. are rounded before welding work is performed. All welds should beinspected and if necessary repaired before cleaning is carried out. The welds must be freefrom weaknesses such as undercut, hole, craters and welding splashes.
Notched, drainage holes etc. should have a radius of at least 50 mm to ensure good primingand correct paint application.
Personal notes
Chapter: Steel work
Jotun Paint school Handouts Page 16
Paint School1
Rounding or smoothing of:Sharp edgesCornersWelds
Grinding of:LaminationsFlame cut edgesWeld spatter
Pre-blasting preparation Pre-blasting preparation involves the following activitiesinvolves the following activities
Notches minimum diameter: 30 mmInspected and approved before cleaning
See ISO 8501 “Visual assessment of surface cleanliness”
Paint School2
A
B
Gas cut edgeA. Remove by grinder or disc sander.
B. Rolled steel sections normally have round edges. Therefore can be left untreated.
A. Remove visible spatter before grit- blasting with grinder or chipping hammer.
B. For spatter not readily removed, remove using grinder/disc.
Sharpedge
Weldspatter
A
B
Steel preparationSteel preparationEdges and weld spatters Edges and weld spatters
Paint School3
Coating applied to a square-cut section
Pre-blasting preparationPre-blasting preparationRounding sharp edgesRounding sharp edges
Reduced coating thickness at sharp edges due to tension created during drying / curing
CoatingSharp edge
Rounded edgeEven coating thickness
Steel
Paint School4
Grinding of sharp edges, welds etc.Grinding of sharp edges, welds etc.Disc sander and disc grinderDisc sander and disc grinder
Sander for removing millscale, paint and rust
Grinder for heavy grinding,such as edges and weld beads
Paint School5
Steel support afterSteel support afterblast-cleaning to Sa 2 ½blast-cleaning to Sa 2 ½
The sharp edges should have been roundedprior to blast-cleaning
Paint School6
Steel support afterSteel support afterblast-cleaning to Sa 2 ½blast-cleaning to Sa 2 ½
The sharp edges have been rounded prior to blast-cleaning:Good !
Chapter: Steel work
Jotun Paint school Handouts Page 17
Paint School7
Manholes in a tankManholes in a tank
• Section manholes• Well grinded edges
Paint School8
Severe corrosion due to aSevere corrosion due to acombination of several effectscombination of several effects
• Sharp edges• Rough welds (not grinded)• Missing stripe coating
Paint School9
Grinding of notch with rotating fileGrinding of notch with rotating file
Easy access with a rotating file
Paint School10
Steel preparationSteel preparationWeld spatter, welding smokeWeld spatter, welding smoke
WeldWeldspatter Areas at risk
Paint School11
Disc grinding of weld beads, sharpDisc grinding of weld beads, sharpedges etc. by means of a disc grinder.edges etc. by means of a disc grinder.
Other types of discs are available.Some of them will reduce the amount of sparks.
Paint School12
Steel substrate after disc grindingSteel substrate after disc grinding
Weld beads etc. has been removedto form an acceptable substrate for the paint system
Chapter: Steel work
Jotun Paint school Handouts Page 18
Paint School13
Remove using grinder
Undercuts exceeding classification rulingshould be repaired by welding and grinding.
Sharp profile peaks to be smoothed usinggrinder
Lamination
Undercut
Manual weld bead
Pre-blasting preparationPre-blasting preparationLaminations, undercuts, welding seamsLaminations, undercuts, welding seams
Paint School14
Unacceptable weld.Unacceptable weld.Too rough and full of pinholes / poresToo rough and full of pinholes / pores
• Weld spatters close to weld• Rewelding and grinding must be carried out
prior to reblasting and painting
Paint School15
Paint on a very poor weld. Pinholes andPaint on a very poor weld. Pinholes andholidays visible after second stripe coatingholidays visible after second stripe coating
• Neither rewelding nor grinding have beencarried out prior to application
• Remedial Actions: Reblasting, rewelding,grinding and blast -cleaning: COSTLY
Paint School16
Early corrosion of welds in aEarly corrosion of welds in awater ballast tankwater ballast tank
• Rough weld seams.Should have beengrinded
• Probably incombination withpoor stripe coating
• Mud can be seen,particularly on thebottom
Paint School17
Not recommended solution for exposure to severe /aggressive environments
Spot welding leads to crevicesSpot welding leads to creviceswhich are susceptible to corrosionwhich are susceptible to corrosion
Paint School18
Sharp edge an spot welds.Sharp edge an spot welds.Early corrosion attackEarly corrosion attack
• Construction newlypainted
• Exposed to humidatmosphere
• Corrosion initiatesafter a short period oftime on weak areas:Sharp edges, crevicesand spot welds
Jotun Paint School Course Handouts Page 19
5. Pre-treatmentAfter the steelwork on the steel structure has been completed, inspected and approved, pre-treatment can begin. The purpose of preparation is to ensure that the substrate is suitable forapplication of the paint, i.e. the steel is sufficiently clean and rough. Contaminants such as oil,grease and salts for example cannot be removed by blast-cleaning. Before preparation begins,the steel must be properly cleaned. Cleaning removes contamination and impurities such asoil, grease, salt, dust and dirt.
Salts from a marine atmosphere which are deposited on the structure, and welding fumes frommanual welding are examples of salts which should be washed off before preparation. Saltscan cause osmotic blistering and oil will reduce the adhesion of the paint. Salts must beremoved with plenty of fresh water. Oil and grease cannot be removed with water alone;strong alkali washing agents and solvents must be used.
Once the substrate is clean, pre-treatment can begin. There are countless methods which canbe used, all of which have advantages and disadvantages. Here is a brief list of some methods:
Blast-cleaning. To ensure maximum paint adhesion, a rough surface is required. In view ofthis, blast-cleaning is the best preparation method. Blast-cleaning removes old paint, rust andscales and gives a clean rough surface. Possible blast-cleaning methods are dry blast-cleaning,slurry blast-cleaning (addition of water) and wet blast-cleaning (water with addition ofabrasives). Dry blast-cleaning gives a clean dry surface and the required roughness but causesconsiderable dust which contaminates the immediate environment. Slurry and wet blast-cleaning give a rough, clean surface without dust, but create flash rust. It has been found thatmuch of the abrasives remain on the substrate after blast-cleaning. Such contaminants may onsome alloys cause a risk of corrosion at these points. For preparation of stainless steel,aluminium and galvanised steel, it is important to use non-metallic abrasives.
Ultra high-pressure water cleaning. This preparation method is becoming increasinglycommon. The method consists of removing contamination, corrosion products and old paintby applying water to the substrate under extremely high water pressure (up to 2500 bar). Themethod has two essential advantages: no cloud of blasting dust is created to contaminate theimmediate environment as in traditional blast-cleaning, and water-soluble salts are removedfrom the substrate. It is important to use clean water so that the substrate is not contaminatedby the water used. The method gives a clean surface but will not give any extra roughness tosteel. The original roughness of the steel is retained where intact paint is removed, but thecorrosion pattern on corroded areas will be considered as roughness where corrosion hasoccurred. One disadvantage with water cleaning is that the tendency to form flash rust on thesteel will increase as moisture is added to the substrate. The degree of flash rust depends onthe relative humidity, the temperature of the steel and atmosphere, and the cleanliness of thesurface.
Mechanical cleaning. Use of mechanical cleaning tools such as steel brushes, grindingequipment or machining, does not achieve the same degree of cleanliness and roughness asblast-cleaning and the adhesion between the substrate and the paint system will therefore bereduced. Needle guns for example often cause excessive roughness or break-up of thesubstrate.
Jotun Paint School Course Handouts Page 20
Electrolytical descaling. There is a special preparation method where magnesium strips areused to remove rust. This has proved particularly useful in severely corroded ballast tanks onsailing ships where thick rust layers can be removed at sea. However, the procedure requires aknowledge of how to calculate the number of anodes needed, installation of the anodes,treatment periods and cleaning after the procedure. Such treatment should therefore be carriedout in collaboration with Jotun.
The method to be used will be described in the paint specification and is primarily selectedon the basis of:
� Purpose of the structure� Exposure conditions� Required life time� Restrictions related to environmental requirements and safety.
One essential element of the entire pre-treatment process is care when performing the work.Today, the inspection is performed with reference to various standards. The most commonstandards are ISO 8501 which gives a visual description of the appearance of a steel surfaceboth before and after blast-cleaning and wire brushing. For water-blasting/water-jetting,separate standards have been prepared by ISO and SSPC/NACE.
Personal notes
Chapter: Pretreatment
Jotun Paint School Handouts Page 21
Paint School1
• Steel work (Pre-blasting preparation)• Removal of:
– Rust and mill scale– Salt– Grease, oil, dirt– Old / unwanted paint
• Flattening of glossy paint• Special pre-treatment of new aluminium
and galvanised surfaces
Surface treatment may include Surface treatment may include the following operationsthe following operations
Paint School2
• Salt and soil: Clean water
• Oil - grease: Solvent with emulsifying agent or alkaline cleaner
Work to be carried out Work to be carried out in the cleaning shopin the cleaning shop
Remove prior to pre-treatment:
Paint School3
Degreasing side bottom with emulsifyingDegreasing side bottom with emulsifyingdetergent to remove oil, grease etc.detergent to remove oil, grease etc.
• Should always be carried out before blast-cleaning• The detergents must be removed by ”Low pressure
water cleaning, LPWC” (Around 250 - 300 bar)
Paint School4
Equipment contaminating the surfaceEquipment contaminating the surfaceOil contamination from grinderOil contamination from grinder
Reasons may be:• Oil leaking out of
equipment• Equipment has been
stored with oil• Lack of oil trap.
(Air from compressorcontains oil)
Must be removed prior to surface preparation
Paint School5
Welding smoke is water solubleWelding smoke is water solubleand can only be removed by waterand can only be removed by water
• Solvents will notremove the weldingsmoke completely
• If not removed,osmotic blisteringmay occur.
Welding smokeArea washedwith water
Paint School6
Blisters close to weld, probably due toBlisters close to weld, probably due towelding smoke remaining on the the steelwelding smoke remaining on the the steel
• Welding smoke is resoluble in water and willcreate osmotic blistering
• Galvanic difference between steel plate and weldmay aggravate the attack
Chapter: Pretreatment
Jotun Paint School Handouts Page 22
Paint School7
Pre-treatmentPre-treatmentEvaluation of methodsEvaluation of methods
Blast cleaningPower grinding
Power wire-brushingManual wire- brushing.Needle hammer
Power chiseling
Manual scraping
IdealNot as good as blast cleaning, but
best alternative.Great risk of unwanted polishing.Not recommended. Very poor.Usable, but risk of unwanted rough
surface,Good in combination with other
methodsUsable in combination with other
methods.
Paint School8
Rotary impact or scarifying toolsRotary impact or scarifying tools
• Peening flaps (Roto-Peen) - Creates a surface profile, 25 to 75 microns• Rotary hammers - cutters• Nylon non-woven abrasive wheels
Rotary impact tools is the best choice for removing coatings
Equipment with rotating abrasive head
Paint School9
Grinders and sandersGrinders and sanders
• Coated abrasive discs- To remove paint, mill scale and rust
• Non-woven abrasive discs- To remove paint and rust and for feathering of paint
• Wire brushes- To remove loose rust (tends to polish surface)
Paint School10
Steel substrate treated by hand andSteel substrate treated by hand andmechanical power tool cleaning equipmentmechanical power tool cleaning equipment
Hand wire brush, approximately St 2
Mechanical wire brush approximately St 3
Paint School11
Pre-treatmentPre-treatmentIllustration of various blasting methodsIllustration of various blasting methods
Paint School12
Dry blastingDry blastingBenefits and limitationsBenefits and limitations
Advantages
• Surface remains dry• Good anchor pattern
for paint• No pre-rusting profile
Disadvantages
• Does not remove salt• Does not remove oil• Creates dust
Chapter: Pretreatment
Jotun Paint School Handouts Page 23
Paint School13
• Productivity is directly proportional to: Pressure at Nozzle Capacity of the air compressor
• Pressure at Nozzle 7 kg/cm² = 100% productivity
• Pressure at Nozzle 5,6 kg/cm² = 66% productivity
• Pressure at Nozzle 4,2 kg/cm² = 50% productivity
Blast cleaningBlast cleaningFactors influencing the production rateFactors influencing the production rate
Paint School14
Nozzle Nozzleholder
Air
Blast - cleaningBlast - cleaningMeasure the air pressure at the nozzleMeasure the air pressure at the nozzle
Rubber hose
Pressure gauge
Paint School15
Blast cleaning: Effect of nozzleBlast cleaning: Effect of nozzlepressure on cleaning rate.pressure on cleaning rate.
Nozzle pressures, Kg / cm²
Cleaning time: 2 minutesSource: Clemtex Ltd.
Remaining Removed
Paint School16
The blast hose shall have an opening which is 3-4 times
bigger than the orifice of the nozzle.
Blast Cleaning Blast Cleaning Rule of thumb: To avoid loss of pressureRule of thumb: To avoid loss of pressure
Hose opening Nozzle opening
3 - 4 times
Paint School17
Corroded area. Subsequent spot blasting
Solid coating
Feathered requiredImpact by abrasives
(SOURCE: Munger, C.G. Practical aspects of Coating Repair.
Materials Performance, Vol. 19, No 2 p. 46 (1980)
Blast cleaningBlast cleaningImpact damages may destroy overlapping zoneImpact damages may destroy overlapping zone
Originally corroded area
Paint School18
Blast cleaningBlast cleaningAbrasives will damage the coatingAbrasives will damage the coating
Cracks due to direct impact by abrasives 3-Coat paint
Corroded and blast cleaned
Area withreduced adhesion
Steel
Area require feathering
Chapter: Pretreatment
Jotun Paint School Handouts Page 24
Paint School19
Blast cleaningBlast cleaningAbrasives will damage the coatingAbrasives will damage the coating
Steel
Areas with reduced adhesion
3-coat paint systemStar crack areasImpact of abrasive
May be caused by direct impact or rebounding abrasives (ricochet)
Paint School20
Blast cleaningBlast cleaningCorrect and incorrect sweep blastingCorrect and incorrect sweep blasting
Star cracks
Abrasives approx. 0.5 mmPressure approx 2-3 kg / sqcm
Often abrasives of 0.2 - 1.4 mm and too high pressure is used
Paint School21
Corrosion has taken placeCorrosion has taken placeAlmost the total area has been spot blastedAlmost the total area has been spot blasted
• Spot blasting in this way result in many looseedges that needs to be feathered
• Recommendation: Blast - clean larger areas
Bare steel
Top coat
Antifouling
Paint School22
Loose edges resulting from spot-Loose edges resulting from spot-blasting carried out some time agoblasting carried out some time ago
• Edges has not been feathered prior to application of the paint• The edges are weak points in the paint film• Corrosion attack initiates on such areas
Paint School23
Surface has not been well cleanedSurface has not been well cleanedOver painting grit or foreign mattersOver painting grit or foreign matters
• Weak point in paint film• Entrapped air• Less adhesion• Corrosion will develop rapidly
Paint School24
Poor cleaning of ballast tanksPoor cleaning of ballast tanks
• Abrasives remaining from blast cleaning• 300 µm Coal Tar Epoxy• Blistering and rust penetration after 10 months of exposure
Chapter: Pretreatment
Jotun Paint School Handouts Page 253
Paint School25
Slurry and wet blastingSlurry and wet blastingBenefits and limitationsBenefits and limitations
Advantages
• Surface profile isachieved
• Removes salt• Creates no dust.
Disadvantages
• Flash rust maydevelop on surface
Paint School26
• Salt level on steel surface drastically reduced.• No dust produced.• No grit cost (water is usually cheaper).
Grit blasting uses 55 kg/m², costing £ 63,-/ton = 3,46/m².Ultra High Pressure Water Jetting, UHPWJ needs 130 l/m²,costing £ 0,80/ton = £ 0,10/m²).
• Close working of other trades possible.• Abrasives can be introduced if improved surface profile is
required.• Lower noise level than with grit blasting.
Water-jettingWater-jettingAdvantagesAdvantages
Paint School27
• Degreasing and washing• Sweep blasting with non-metallic abrasive• Abrading through other means, e.g.
mechanical tools, emery paper etc
Pre-treatment ofPre-treatment of Stainless steelStainless steel
Paint School28
• Degreasing and washing• Sweep blasting with non-metallic abrasiveor• Abrading through other means, e.g.
mechanical tools, emery paper etcor• Washing with a strong alkaline cleaner
followed by washing with clean wateror• Wash primer (Not in combination with
Epoxy paint)
Pre-treatment ofPre-treatment of AluminiumAluminium
Paint School29
Pre-treatment of hot-dipPre-treatment of hot-dipgalvanised steel.galvanised steel.
• T-wash• Sweep blasting• Etch primer, single or two - pack• Natural weathering for at least
twelve months
Paint School30
Electrolytic de-scaling.Electrolytic de-scaling.Working processWorking process
• Empty the ballast tank• Mount the Magnesium strips• Fill the tank with seawater• Ballasting period of 1-2 weeks• Empty the tank• Remove calcareous deposit immediately
(Water pressure: 250 to 300 bar)• Remove loose rust and scale• Remove iron cores• Dry the tank• Start application of paint
Jotun Paint School Course Handouts Page 26
6. Paint ApplicationIt is important to understand that paint is a semi-finished product. Only once the paint hasbeen applied to a structure will the real properties of the paint system become apparent. Howwell a system works largely depends on the skill of the painter. The protective properties of apaint can be significantly reduced if the paint is applied incorrectly.
Application technique
To apply the paint to achieve the optimum properties, it is important to select the rightapplication tool and method. Generally application tools are selected according to the size ofthe object, complexity, accessibility, type of paint and environmental aspects.
Painting always begins with "stripe coating". Stripe coating means applying an extra coat ofpaint on areas where experience has shown that it is difficult to achieve the specified filmthickness by spray. Typical areas which should be stripe coated are sharp edges, notches,welds (particularly manual welds) and areas which are difficult to reach with a spray gun.This is a very important job but it is often skipped or done badly as it is a time-consumingprocess. Stripe coating on bare steel should always be carried out with a round or oval brushand not a roller. The aim is to ensure good wetting of the substrate. Stripe coating should alsobe used between each coat. A stripe coat can be applied with a roller on the previous coatwhere suitable. The film thickness achieved using brushes or rollers is normally in the rangeof 35 - 40 µm.
Airless spraying is the most effective and cost-saving application method. It is possible topaint large areas in the minimum of time and paint can be applied in greater and more evenfilm thicknesses per coat than with a brush and roller. The application technique andexperience of the painter are very important for achieving a good result. This includes factorssuch as the right distance between the gun and object (normally 30 to 60 cm), the right angleto the object (normally 90 degrees), good overlapping (approx. 50% overlap) and sensitivityin use of the trigger. When spraying, the paint is applied at as low a pressure as possible toachieve an even spread. Too high a pressure leads to dry spraying and a lot of dust.
Checks to be carried out during application
The painter only has one instrument available for checking the film thickness duringapplication: wet film gauge (comb or wheel). It is important to use the cam regularly. Thisensures good checking during the entire application process so that the correct film thicknessis achieved over the entire structure. The atmospheric conditions should always be checkedduring application of paint, and the correct ventilation ensured, especially in tanks. Theseconditions must be monitored throughout the application process and whilst the paint isdrying / curing.
Mixing and thinning
Do not add unnecessary quantities of thinner to the paint as this causes slower drying and youwill have to apply the paint in greater wet-film thicknesses to achieve the same dry film. Use
Jotun Paint School Course Handouts Page 27
of the correct (specified) thinners is important as adding the wrong thinner can cause poorresults in terms of corrosion protection.
When applying two-component paints, the mixing process itself is also important. Usemechanical agitators and not stirrers. Good agitation or mixing of the two components and thecorrect mixing ratio are important. Follow the instructions on the technical data sheet for theproduct. Plural component spray (two-component spray) are also available for applyingspecial two-component paints, where the components are mixed in the correct ratio in the unititself.
Health
The painter is exposed to solvents and various other components in the paint. Make sure thatapproved protective equipment is used and that ventilation is adequate.
Personal notes
Chapter: Paint Application
Jotun Paint School Handouts Page 28
aint School1
ApplicationApplication
Cleanliness and good housekeeping before,during and after application are one of the most
important factors to have a good result
Paint School2
Tools for mixing of paintsTools for mixing of paints
• Always use mechanicalagitator to ensure propermixing.
• Proper mixing will not beachieved by a stirrer
• A stirrer may also containdirt and loose parts thatmay contaminate the paintand clog the sprayequipment
Paint School3
Consequence of inferior mixing:Consequence of inferior mixing:Poor coating performancePoor coating performance• To the right: Correct mixing and mixing ratio.• To the left: Insufficient mixing and / or incorrect
mixing ratio.
Paint School4
Airless spray:Good
Paint brush:Good
Roller:Poor, particularly for the first coat
Methods for paint applicationMethods for paint application
Paint School5
Application by paint brushApplication by paint brush
Benefits• Good wetting of the substrate• Forces the paint into the surface• Better than roller on the first coat• Good on areas with poor accessibility
Limitations• Gives low film thickness, many coats required• Creates an uneven film• Application speed is slow
Paint School6
Benefits• Application speed is faster than with paint brush• Good on areas with poor accessibility
Limitations• Poor wetting of the substrate• Never use for the first coat• May incorporate air and pinholes in the paint film• Gives low film thickness, many coats required
Application by rollerApplication by roller
Chapter: Paint Application
Jotun Paint School Handouts Page 29
Paint School7
ApplicationApplicationStripe coating prior to each full coatStripe coating prior to each full coat
• Where difficult access with spray• Profiles • Inside edges• Holes, notches• Corners, angles• Sharp edges • Manual welding seams
Stripe coat with paint brush:
Paint School8
Stripe coating of superstructureStripe coating of superstructurebetween first and second full coatbetween first and second full coat
• Pipes• Supports• Windows• Reeling
Note the contrasting colours.Excellent work
Paint School9
Poor workmanship:Poor workmanship:Stripe coated welding seamStripe coated welding seam
• Many holidays• The paint must be worked properly into the rough
substrate using several strokes with the paint brush.
Paint School10
• Correct distance between spray gunand substrate: (30-60 cm)
• Correct angel (90°)
• Overlapping (50% or cross application)
Paint application.Paint application.Rules when sprayingRules when spraying
Paint School11
Seek to keep the gun at aSeek to keep the gun at aright angle to the substrateright angle to the substrate
The distance should be between 30 and 60 cm. The optimaldistance will vary, among other things with wind,
temperature, pressure at the nozzle and viscosity of the paint .
Paint School12
50 %
OverlapOverlapping ensures an even film thickness
Paint application. Paint application. Airless spraying with overlapAirless spraying with overlap
Chapter: Paint Application
Jotun Paint School Handouts Page 30
Paint School13
Application with a spray gun.Application with a spray gun.Stroke and triggeringStroke and triggering
Start stroke →→→→ Pull trigger →→→→ Release trigger →→→→ End stroke
Structure
Paint School14
• As the coating droplets hit the substrate they will become flat. • Then, they will overlap and form a continuous paint film
Formation of a paint filmFormation of a paint film
Paint School15
Area of effective spraying
Outside area of effective spraying:• Low impact• Poor flow of paint• Result: Dry-spray
Overspray or dry-sprayOverspray or dry-spray
Dry-spray will develop at the edges of a wide spray fan.This may give a rough film and pinholes
Paint School16
Incorrect application technique.Incorrect application technique.Waving with the gunWaving with the gun
Result:• Uneven paint film• Dry-spraying will occur• The loss factor will be high• The roughness will increase
Paint School17
• A rough surface• Too much paint dust• Pinholes in the paint film• Entrapped air• Entrapped solvents• Too high paint consumption
Incorrect use of airless spray Incorrect use of airless spray equipment will result in:equipment will result in:
Paint School18
Spraying of a ship’s bottom.Spraying of a ship’s bottom.Very poor application techniqueVery poor application technique
• Too long distance• Dry spraying• Uneven film thickness
Running wateralong side the shipwhile painting.(Scupper plug missing)
Chapter: Paint Application
Jotun Paint School Handouts Page 31
Paint School19
Poor application techniquePoor application techniqueserves nobodyserves nobody
• Contamination ofthe environment
• High loss factor• Poor corrosion
protection• Waste of money
Paint School20
Spot-blasting andSpot-blasting andpoor application technique.poor application technique.
• Loose paint edges• Application has been
done in only onedirection
• Corrosion hasdeveloped on shadowsides shortly afterapplication
Direction of application
Paint School21
Application TechniqueApplication TechniqueWith Spray GunWith Spray Gun
Positioning of the spray gunCorrect Wrong
Parallel Perpendicular Arcing Tilting
Over spray Heavy Light
Light
Paint School22
Source: Corr. Control Principles and Metodes, Sect. 7, Ameron Inc., Monterey Park, Ca.)
Spray application technique.Spray application technique.Apply one extra coat to cornersApply one extra coat to corners
Wrong Correct
Paint School23
Application directly into the corner gives an uneven film thickness,but may still be satisfactory for many types of service
(Source: Industrial Maintenance Painting, National Association of Corrosion Engineers; Houston TX, p. 88, 1973.)
Area with thick paint film
Area with thin layer of paint
Application of inside cornersApplication of inside corners
Air cushion is formed
Paint School24
(Source: Industrial Maintenance Painting, National Association of Corrosion Engineers; Houston TX, p 88, 1973)
1
23
54
Application of inside cornersApplication of inside corners
• Spray each side of the corner separately• Use a vertical spray pattern• This will give an even film thickness
Chapter: Paint Application
Jotun Paint School Handouts Page 32
Paint School25
Air will be compressed in pits and push the paint back.This makes use of airless spray on such areas almost impossible
Application technique:Application technique:
Surfaces with deep pitsSurfaces with deep pits
Paint School26
Inside a tankInside a tankRuns leading to cracking of paintRuns leading to cracking of paint
• Paint has collectedin the corner
• Several mm thickpaint
• The paint cracked,corrosion willdevelop
Paint School27
Paint not applied according to thePaint not applied according to thespecification. Close up of paint filmspecification. Close up of paint film (2 of 2)(2 of 2)
• Specification : 50 µm• Thickness of topcoat:
100 - 150 µmResult:• Entrapped air• Entrapped solvents• Porous film• Blisters and
delamination willoccur in future
Paint School28
• Relative humidity, %• Ventilation• Temperature• Film thickness• Number of coats• Evaporation speed of solvents
What factors influenceWhat factors influencethe drying / curing process ?the drying / curing process ?
Paint School29
Temperature of substrate should be ata temperature of
min. 3oC
above dew point of the air in thevicinity
Main rule for pre-treatment Main rule for pre-treatment and paint application:and paint application:
Paint School30
Temperature and humidityTemperature and humidityof air used for drying.of air used for drying.
• Supply of heated air immediately after application maylead to skin drying and entrapped solvents
• Cold air will keep the film open longer and ensure properevaporation
• Avoid high air temperature (especially epoxy)• High humidity will slow down the drying time• Exhaust from heating equipment using propane or paraffin
oil contain water and Carbon dioxide and may createAmine sweating
Jotun Paint School Course Handouts Page 33
7. Inspection and ControlThe human factor is an important element in the process to ensure the specified quality of thepaint system. It is therefore very important to inspect and control all work performed inconnection with surface treatment. During the manufacture of a structure, inspections andcontrol should be performed at the following critical phases:
• Steelwork• Pre-treatment• Before, during and after application.
For all activities, the inspector should verify and document that the work complies with thespecification and has been performed professionally, and that the paint supplier's instructionsfor use of the product have been followed.
Steelwork
Activities which are normally included in the preparation are described in chapter 4. Theinspector should verify that the steelwork has been performed according to specification orISO 12944-3. In particular, this includes the rounding of edges, grinding of welds, removal ofweld spatters and grinding of laminations.
Pre-treatment
The inspector must check and ensure that the structure is free from oil, grease and salt andthat the washing procedure has been followed. Visual assessments shall be made of the degreeof rust on the steel before preparation and the condition of the structure after preparation.Standards ISO 8501-1 or ISO 8501-2 (for repair work) apply. Before and during pre-treatment, the atmospheric conditions are checked according to ISO 8502-4. Other checks tobe performed usually include inspection for invisible contamination on the surface such assalts (ISO 9502-6 and 9), dust (ISO 8502-3) and specified roughness (ISO 8503). All data andrecords shall be entered in a daily log.
Application of paint
The inspector's task during application of the paint is to ensure that all work proceeds in thespecified manner. This includes all work operations from opening of the paint tin to theapplication of the final coat. It is important to have a good overview of all technicaldocumentation. Check technical data sheets and check for use of the right thinners, the rightcuring agent for the base, mechanical agitators and a good mix when using two-componentpaints. Check the specified pre-reaction time if given in the technical data sheet. Check thatstripe coating has been performed properly before application of the full coat by spraying.Ensure that the painter carries out careful checks with using wet film gauge so that thespecified wet film thickness is applied. The atmospheric conditions should be monitoredduring the painting work. Ensure adequate ventilation to remove solvents. All data andrecords must be entered in a daily log.
Jotun Paint School Course Handouts Page 34
Drying / curing
After drying / curing, the dry film thickness is checked (ISO 2808). Pay particular attention toareas where access with an airless spray gun is difficult, and ensure that the dry film thicknesslies within the specified limits. Check that the overpainting intervals are observed for thepaints, and that the surface is clean before overpainting. After a structure is painted, the totalfilm thickness should be checked. Individual specifications also require adhesion testing forexample to ISO 4624, or holiday detection to ASTM G62-85. It is very important to havegood test routines and enter all data and records in a daily log.
Personal notes
Chapter: Inspection and Control
Jotun Paint school Handouts Page 35
Paint School1
What is QA - QC ?What is QA - QC ?
QA = Quality Assurance (A documented management system)
QC = Quality Control (Inspection and testing routines)
Paint School2
An inspector’s work includes:An inspector’s work includes:
• Be capable of interpreting the specifications• Understand the objective of the inspection• Inspect all structures to be painted• Ensure that all specified requirements are met• Document the results from the inspections• In case of non-conformance: Issue written reports
Paint School3
Daily logsDaily logs
• Steel temperature• Air temperature• % Relative Humidity• Dew point• Object no. and name• Exact specification• Pre-treatment, specified and
actually conducted.
• Film thickness (to bemeasured also at spot repair)
• Area, m²• Product name, place of
production and batch no.• Name of relevant persons• What was discussed• Non conformance report
(remember signatures)• Other comments
Paint School4
• All paints that will be used• All relevant inspection methods and inspection tools• Relevant standards• Relevant TDS and MSDS• Methods involved in cleaning, pre-treatment
and paint application• The equipment used for pre-treatment and
application: Benefits and limitations
An inspector needs to knowAn inspector needs to know
Paint School5
What needs to be inspected ?What needs to be inspected ?
• Shop-priming of the steel• The steel work (Pre-blasting preparation)• Cleaning and surface preparation
prior to paint application• Application of paint• The applied paint film and its
curing/drying conditions.
If relevant, the following stages of the production need to be inspected
Paint School6
Inspection of steel workInspection of steel work(Pre-blasting preparation)(Pre-blasting preparation)
• Rounding of sharp edges.• Smoothing of rough welding seams.• Removal / grinding of weld spatter and beads.• Cracks and pittings.• Surface faults like laminates etc.• ISO 12944 - 3 , or ISO 8501 - 3
The following items need to be inspected during construction
Chapter: Inspection and Control
Jotun Paint school Handouts Page 36
Paint School7
Inspection of cleaning and surfaceInspection of cleaning and surfacepreparation prior to applicationpreparation prior to application
• Cleanliness (salt, oil, grease and dust/dirt)• Evaluation of present condition (rust grade)• Surface preparation (e.g. blast cleaning)• Cleanliness of prepared surface
(salts, oil, grease, dust and dirt)• Climatic conditions
(temperature, relative humidity etc.)
If relevant, the following conditionsmust be inspected / verified
Paint School8
ISO 8501 - 1ISO 8501 - 1Surface preparationSurface preparation
• Visual assessment of surface cleanliness after blast cleaning, hand or power tool cleaning or flame cleaning
• Rust grades and preparation grades of uncoated steel
• Photographic examples of steel when blast cleaned with different abrasives
Paint School9
ISO 8501 - 2ISO 8501 - 2Surface preparationSurface preparation
As for ISO 8501-1, but: For steel where previous coating has been removed
locally, not completely.
Paint School10
PSa : Localised blast cleaning (grades 2, 2 ½ and 3)
PSt : Localised hand and power tool cleaning (grades 2 and 3)
PMa : Localised machine abrading (one grade)
ISO 8501 - 2ISO 8501 - 2Standard for deciding preparation gradesStandard for deciding preparation grades
Paint School11
ISO 8502ISO 8502Assessment of surface cleanlinessAssessment of surface cleanliness (1 of 2)(1 of 2)
Part 1 Field test for soluble iron corrosion products
Part 2 Laboratory determination of chloride on cleaned surfaces.
Part 3 Assessment of dust on steel surfaces prepared for painting (pressure- sensitive tape method)
Part 4 Guidance on the estimation of the probability of condensation prior to paint application.
Part 5 Measurement of chloride on steel surfaces prepared for painting. Ion detector tube method.
Paint School12
ISO 8502ISO 8502Assessment of surface cleanlinessAssessment of surface cleanliness (2 of 2)(2 of 2)
Part 6 Extraction of soluble contaminants for analysis. The Bresle method.
*Part 9 Conductometric measurements of soluble salts
.
* Part 7, 8 and 10 are not prepared
*
Chapter: Inspection and Control
Jotun Paint school Handouts Page 37
Paint School13
Surface temperature of the
structure must be minimum
3 °C above the dew point
of the surrounding atmosphere
Atmospheric conditions.Atmospheric conditions.Requirement during blasting and paintingRequirement during blasting and painting
Paint School14
• Ambient temperature will influence:– shelf life– pot life– viscosity/sprayability– steel temperature
• Steel temperature will affect:– speed of cure– degree of cure– recoating interval– service life of the coating
Ambient temperature andAmbient temperature andsteel temperaturesteel temperature
Is the temperatures important ? YES !
Paint School15
ISO 8502 - 6ISO 8502 - 6The Bresle method.The Bresle method.
A method for extraction ofsoluble contaminants on
steel substrates for analysis:
The Bresle method
This is a quantitative test
Paint School16
ISO 8502 - 9ISO 8502 - 9ConductometricConductometric measurement of soluble salts. measurement of soluble salts.
Field method for measuring soluble saltsby conductivity (µ S) of solutions
containing water soluble salts
Paint School17
Calculation of salt levelCalculation of salt levelon the substrateon the substrate
(L(L22 - L - L11) x 6 = mg salt per m) x 6 = mg salt per m22
L2 = µS after cleaning
L1 = µS before cleaning
Water sample, ml.: 10 15 20 50Constant in formula: 4 6 8 20
Formula:
Paint School18
Instruments for measuringInstruments for measuringsurface roughnesssurface roughness
• Stylus instruments• Elcometer Mod. 123• Testex Press-O-film• Microscope• Comparator
–Rugotest No. 3–ISO 8503 etc.
Chapter: Inspection and Control
Jotun Paint school Handouts Page 38
Paint School19
ISO 8503ISO 8503Surface roughnessSurface roughness
• Example of a referencecomparator
• Surface profile comparatorcomprising four segments.
• Grit (G)• Shot (S)• Check if the profile is
according to specificationand the paintmanufacturer’srecommendation
Paint School20
Inspection during applicationInspection during application
• Record name of coating and batch no.• Ensure proper mixing of 2-pack paints• Ensure use of the correct thinner• Measuring the wet film thickness (WFT)• Number of coats as given in the specification• Cleanliness between coats (salts, dust, oil etc.)• Drying time / recoating intervals• Control of equipment: Pressure, nozzle etc.• Climatic conditions (Ventilation, Air and steel temperature and the relative humidity)
The following must be verified, inspected or tested:
Paint School21
Information to be found from theInformation to be found from thetechnical data sheet, TDStechnical data sheet, TDS
• Product description– Generic type etc.
• Recommended use– Where to use the product
• Technical information– Solids by volume, WFT,
DFT• Application data
– Methods, mixing, potlife• Surface preparation
– Different methods given
• Conditions duringapplication
• Drying and overcoating timeat different temperatures
• Typical recommendedsystem
• Storage• Handling• Packing control• Health and safety
– Details in MSDS
Paint School22
Method 1:
Method 2:
Method 3:
Method 4:
Method 5:
Determination of wet film thickness.
Determination of dry-film thickness bycalculation from mass
Measurement of dry-film thickness bymechanically contacting method
Measurement of dry-film thickness by theprofilometer method
Measurement of dry-film thickness usingmicroscope method
ISO 2808 - 97ISO 2808 - 97Determination of film thickness Determination of film thickness (1 of 2)(1 of 2)
Paint School23
Method 6:
Method 7:
Method 8:
Method 9:
Method 10:
Magnetic method
Eddy current method
Non-contact methods
Gravimetric method (dissolving methods)
Determination of dry-film thickness onblast-cleaned steel substrates
ISO 2808 - 97ISO 2808 - 97Determination of film thickness: Determination of film thickness: (2 of 2)(2 of 2)
Paint School24
Calculations : PaintCalculations : PaintAbbreviationsAbbreviations
WFT = Wet Film ThicknessDFT = Dry Film Thickness% VS = Percent Volume SolidsLF = Loss FactorDV = Dead Volume
Chapter: Inspection and Control
Jotun Paint school Handouts Page 39
Paint School25
Example:
WFT = 250 µm
% VS = 50 %
DFT = = 125 µm
WFT x % VS100
250 x 50100
Formula for determining the DFTFormula for determining the DFT
Formula: DFT =
Paint School26
Consumption of Paint with lossConsumption of Paint with loss
Epoxy mastic = 196 litre
Polyurethane topcoat = 83 litre
500 x 200 10 x 85 x 0,6
500 x 50 10 x 50 x 0,6
To be painted: Tank, area of 500 m2 , 40 % loss
40 % loss implies that only 60 % will remain on the surface. The correction factor, Loss factor, will be 0.6
Formula: Area, m2 x DFT 10 x % VS x loss factor
Paint School27
Dead volumeDead volume increases theincreases thevolume of paint requiredvolume of paint required
Steel
Smooth (polished) steel surfaceEven film thickness
Steel
Uneven steel surfacePaint will fill the valleys
Specified thickness
Dead volume
Paint School28
How much paint should we order ?How much paint should we order ?calculation of paint consumption with losscalculation of paint consumption with loss
Example: 100 litre is needed, loss is 40 %We have to order
= = 167 litre
Not 100 litre + 40 % extra = 140 litre
100 x 100 60
100 0,6 (loss factor)
A loss of 40 % means that only 60 % will be applied on the surface
Paint School29
Inspection after applicationInspection after application
• Climatic conditions (Ventilation, Temperature and humidity)• Curing / drying of the film• Dry film thickness (DFT)• Adhesion• Holiday detection (if required)
After application the following must be checked
Paint School30
• Electromagnetic instruments• Calibration on a smooth steel surface min. 1,2 mm thick• For DFT measurement, not less than 25 and preferably
above 50 microns• Number of readings, as a guide:
– 1 reference area: At least 3 readings evenly– 2 reference areas for every square meter for flat plates– 4 reference areas for every length for a web– 2 reference areas every metre length for a flange– 2 reference areas every metre length for a pipe
ISO 2808 - 97ISO 2808 - 97Determination of film thicknessDetermination of film thickness
Method No. 10 - On blast cleaned steel substrates
Chapter: Inspection and Control
Jotun Paint school Handouts Page 40
Paint School31
ASTM D 3359-87ASTM D 3359-87Adhesion testing by knife and adhesive tapeAdhesion testing by knife and adhesive tape
• There are two test methods• The method to select depends on the DFT
Method A: DFT above 125 micronsMethod B: DFT below 125 microns
(Above 125 if wider cuts are used)
Method A: X - cut. Tape testMethod B: Cross - cut. Tape test
Paint School32
ISO 2409ISO 2409Cross-cut testCross-cut test
Cutting toolSingle bladed knife
orMulti-blade cutting tool with 6 cuttingedges spaced 1 mm or 2 mm apart
Spacing of cuts 0 - 60 microns: 1 mm spacing, hard substrates 0 - 60 microns: 2 mm spacing, soft substrates60 - 120 microns: 3 mm spacing, hard/soft substrates121 - 250 microns: 3 mm spacing, hard/soft substrates
Paint School33
ISO 4624ISO 4624Pull-off test for adhesionPull-off test for adhesion
Procedure:• Test dollies glued onto the coating• Adhesive: Cyano-acrylate or solvent free epoxy• Remove adhesive and coating around the dollies• Pull off test-dollies vertical to the surface• Read adhesion value and report the type of fracture
Fractures:• Adhesion failure - fracture between coats or substrate and 1. coat• Cohesion failure - fracture within a coat
Paint School34
ASTM G 62 - 85 Method AASTM G 62 - 85 Method APinhole detection. Pinhole detection. LowLow voltage.voltage.
• Low voltage: < 75 V DC• To detect pinholes, voids or metal particles to be
in the range of 25-250 microns.• Effective for paint films up to a DFT of 500
microns if a wetting agent is used in the water.• This is a non-destructive test.
Paint School35
ASTM G 62 Method BASTM G 62 Method BHoliday detection. Holiday detection. High High voltage.voltage.
High voltage: 900 - 20.000 V
Used to detect pinholes, voids andareas with thin paint films
This is a destructive test.
Paint School36
ISO 12944ISO 12944General standard for corrosion protection:General standard for corrosion protection:
Part 1 General introduction.Part 2 Classification of environments.Part 3 Design considerations.Part 4 Types of surface and surface preparation.Part 5 Protective paint systems.Part 6 Laboratory performance test methods.Part 7 Execution and supervision of paint work.Part 8 Development of specifications for new work
and maintenance.
Paints and varnishes - Corrosion protection of steel structures by protective paints systems.
Jotun Paint School Course Handouts Page 41
8. Paint FailuresAs we have already said, paint supplied in containers is a semi-finished product. The finishedproduct only exists once the paint has been applied to the structure in a complete paint system.This is where we see how good the protection is. The most important and most common paintfailures occur as a result of poor or insufficient steelwork, preparation or application. Some ofthese faults are revealed during or shortly after application but some only appear after acertain period in service. The most common failures during and just after application are:
• Insufficient film thickness• Sags / runs• Dry spraying• Pinholes• Amine sweating
Insufficient film thickness is often the result of non-systematic application and inadequatechecks with a wet film gauge.
Sags / runs occur when the paint is applied too thickly or too much thinner has been added tothe paint. This is probably because the specification has not been followed. Occasionally,faults are also found in the paint. The inspector must note the production number in the dailylog. Sags / runs should be repaired immediately with a brush.
Dry spraying is normally a result of poor application or difficult weather conditions. Themost common application fault is too great a distance between the spray gun and the structure.High temperature combined with low relative humidity will also contribute to dry spraying asthe solvents evaporate en route from the gun to the object. Strong wind or strong ventilationalso contributes to an increased risk of dry spraying.
Pinholes often occur on porous substrates, for example zinc silicate. On these substrates, it isimportant to apply a thin layer of paint, normally called a tie coat or by using the mist coat -full coat technique. Pinholes are also found if there is too strong ventilation duringapplication.
Amine sweating can occur on epoxy paints during curing in particularly humid environments.The phenomenon results in a sticky surface, occasionally visible as white stains. These mustbe removed before overpainting using rags and tepid water (thinners for some paints). Therisk of amine sweating is reduced by observing the specified induction time after mixing thetwo-component paint and ensuring good atmospheric conditions during application andcuring.
The most common paint faults after exposure are:
• Blistering• Rust penetration• Cracking• Flaking• Chalking
Jotun Paint School Course Handouts Page 42
Such faults can be assessed using standard ISO 4628.
Blistering is normally an adhesion-related problem and is due to poor cleaning beforeapplication of the paint. The most common cause of blistering is the application of the paint toa substrate contaminated with salt (osmotic blistering). After blisters have formed, they burstand the underlying unprotected material begins to rust if rust formation has not alreadystarted. Osmotic blistering occurs on exposure under water or in areas with heavycondensation. In particular, the salts sodium chloride and ferric chloride, and welding smoke,cause blistering. Other causes of blistering can be dust or grit on the surface (reducesadhesion), voids between the steel and the paint or trapped air in the paint film. Blistering isevaluated according to ISO 4628-2.
Rusting occurs after a blister in the paint film bursts. The failure will occur most quicklywhere the paint film is too thin. Particularly susceptible areas are sharp edges, rough weldsand places which are difficult to access for application. If rusting occurs after a very shorttime without prior blistering, there will be an opening through to bare steel, i.e. a pinhole.Rust penetrationevaluated according to ISO 4628-3.
Cracking occurs after a certain ageing of the coating. The causes can be:
• The top coat is harder than the coats underneath• Excessively thick system combined with temperature variations• Excessively fast curing of two-component systems• Excessively thick zinc silicate gives "mud cracking".
There are various degrees of cracking. Cracks can either form in the top coat only orthroughout. The time before the fault occurs can vary. Mud cracking occurs immediately afterapplication but cracking occurs only after a certain time. Cracking is evaluated according toISO 4628-4.
Flaking is normally the result of a poorly cleaned substrate (oil, grease) or the paint beingapplied onto condensation or surfaces with amine sweating. Paint will frequently flake offfrom areas with blistering or cracking and occurs where adhesion is poorest. Flaking isevaluated according to ISO 4628-5.
Chalking is an ageing problem. The binder is degraded by UV radiation from the sun and thepigments appear as dust on the surface. The paint's ability to resist chalking will varyaccording to the binder used. Epoxy will chalk in sunlight after just a few months whereaspolyurethane will retain its gloss for many years. Chalking is evaluated according to ISO4628-6.
Personal notes
Chapter: Paint Failures
Jotun Paint school Handouts Page 43
Paint School1
Most common paint failuresMost common paint failures
• Holidays, too low DFT• Sags and runs• Orange peel• Dry spraying• Overspray• Pinholes, popping• Fish-eyes• Wrinkling / lifting
• Sweating (Amine)• Blushing• Poor drying / curing• Blisters• Rust penetration• Cracking• Flaking• Chalking• Discolouration/bleeding
Paint School2
Sags and runsSags and runs
Appearance• Paint running or hanging like curtains on vertical surfacesCaused by• Too high Wet film thickness• Too much thinner added to the paint• Airless spray gun too close to surfaceRepair• Avoid above• Use paint brush to smoothen or remove excessive paint
Paint School3
Orange peelOrange peel
• Paint surface is rough, like an orange peel
• Poor flow / levelling properties of the paint(Paint too thick or too low temperature)
• Poor atomisation of the paint• Too fast evaporation of the thinner• Airless spray gun too close to surface
• Improve application technique• Use correct thinner• Grind surface and apply new paint
Appearance
Caused by
Repair
Paint School4
Dry sprayDry spray
• Porous, sandpaper like surface of the paint• Poor atomisation of the paint• Spray gun too far away from the object• High air temperature and low relative humidity: Too fast
evaporation of the solvents• Strong wind during application• Inorganic Zinc: Re-blast and apply new paint• Physically drying paints: Apply thinner on the painted
surface and apply a new coat• Oxidativly drying paints: Remove loose dust and apply
topcoat• Two-pack paints: Remove loose dust, sandpaper to
smooth surface, apply topcoat
AppearanceCaused by
Repair
Paint School5
PinholesPinholes
Appearance• Tiny holes through one or more coats, or even down to the
substrate, as if perforated by a needleCaused by• Dry spraying• Entrapped solvents or air• Porosity of previous coat• Incorrect application technique or viscosity of the paintRepair• Grind top layer of the paint• Recoat
Paint School6
Pinholes / poppingPinholes / popping
Solvents or air try to evaporate through the upper partof the film, which has already nearly dried, leavingsmall bubbles /craters on the surface
• Very porous substrate (e.g. Zinc silicate primer)• Entrapped solvents or air in the paint film• Usually in connection with too high film thickness,
too long application distance or too strong ventilation.
• Reduce film thickness or ventilation and adjustapplication technique (Tie coat / mist coat technique.
• Remove paint on painted surfaces and repaint
Appearance
Caused by
Repair
Chapter: Paint Failures
Jotun Paint school Handouts Page 44
Paint School7
FisheyesFisheyes
Appearance• Spots of paint on the surface with no wetting of the
surface around the spots. Appearance of a fisheye.Caused by• Paint applied on oil, silicone or other contaminants• Painted on incompatible paint (Glossy paint giving
poor wetting)Repair• Grind top layer of the paint• Recoat
Paint School8
WrinklingWrinkling
Appearance• Small wrinkles through or partly through the paint filmCaused by• Skin drying of the paint film, which is usually applied
too thickRepair• Grind top layer of the paint• Recoat
Paint School9
LiftingLifting
Appearance• Small wrinkles through the paint filmCaused by• Softening and raising or swelling of a previous
coat by the application of an additional coat• Normally when overcoating Alkyd• Lifting often caused because the solvents in the
new coat is too strong for the previous coatRepair• Remove the paint• Recoat
Paint School10
Sweating and carbonisationSweating and carbonisation(Amine blooming)(Amine blooming)
Appearance• Tacky and sweating film, often with white stainsCaused by• High humidity, particularly on Epoxies during curing• Poor ventilation• The Amines react with CO2 and humidity and form
Amine carbamate.• Too low temperatureRepair• Wash with warm water or thinner, using ragsPreventive measure: Induction time before application start
Paint School11
Bloom and blushBloom and blush(Blushing)(Blushing)
Appearance• Surface looks milkyCaused by• Condensation on cold steel surfaces at high humidity• Air pollution, sulphur dioxide (SO2) and ammonia
forming ammonium sulphate on the paint film.• “Fast “ thinnersRepair• Grind top layer of the paint• Recoat
Paint School12
ISO 4628ISO 4628Content of the StandardContent of the Standard
Part 1 General principles and rating schemesPart 2 Designation of degree of blisteringPart 3 Designation of degree of rustingPart 4 Designation of degree of cracking
Part 5 Designation of degree of flakingPart 6 Designation of degree of chalking
The standard consists of six parts
Chapter: Paint Failures
Jotun Paint school Handouts Page 45
Paint School13
ISO 4628 - 2ISO 4628 - 2Degree of blisteringDegree of blistering
Density 2 Density 3
Density 4 Density 5
Blisters of size 5
Paint School14
ISO 4628 / 3ISO 4628 / 3Designation of degree of rustingDesignation of degree of rusting
RatingDesignate the degree of rust formation byreference to the pictorial standards
Degree Area rusted %Ri 0
Ri 1
Ri 2
Ri 3
Ri 4
Ri 5
0
0,05
0,5
1
8
40/50
Paint School15
ISO 4628 / 3ISO 4628 / 3Designation of degree of rustingDesignation of degree of rusting
Test report:The test report shall contain at least the following information:a) the type and identification of the product testedb) a reference to this International Standard (ISO 4628/3)c) the numerical rating of the rusted aread) the numerical rating of the size of the rust spots, if desired, for example: Rust: Ri 3 (S4) = rusted area, as a percentage of rust, approximates standard 3,
the sizes of the individual rust spots of the order of a fewmillimetres.
e) the date of the examination
Paint School16
Pinpoint rustingPinpoint rusting
Appearance• Points of rustCaused by• Small pores (pinholes), openings or defects in
the paint film down to bare steel• Holidays due to overspray, dry spraying etc.• Too high substrate roughnessRepair• Grind down to bare steel• Recoat
Paint School17
ISO 4628 / 4ISO 4628 / 4Designation of degree of crackingDesignation of degree of cracking
Test report:a) the type and identification of the product testedb) a reference to this International Standard (ISO 4628/4)c) the numerical rating of the quantity of crackingd) the numerical rating of the size of crackinge) the depth of cracking (a. b. or c), where possible, for example: cracking 2 (S3) b
If necessary, the standard assessment may be amplified inwords, for example “linear cracking”. The use of suchcomments shall, however, be avoided wherever possible
e) the date of the examination
Paint School18
ISO 4628 - 4ISO 4628 - 4Evaluation of crackingEvaluation of cracking
Quantity
1 2 3 4 5
Chapter: Paint Failures
Jotun Paint school Handouts Page 46
Paint School19
ISO 4628 / 5ISO 4628 / 5Designation of degree of flakingDesignation of degree of flaking
Test reportThe test report shall contain at least the following information:
a) the type and identification of the product testedb) a reference to this International Standard (ISO 4628/5)c) the numerical rating of the quantity of flakingd) the numerical rating of the size of flakinge) the depth of flaking (a or b),
for example: flaking 3 (S2) a
Paint School20
ISO 4628 - 5ISO 4628 - 5Evaluation of flaking.Evaluation of flaking.
Quantity
1 2 3 4 5
Paint School21
ChalkingChalking
• Almost like dust on top of the coat• The gloss will be reduced
Pigments and extenders exposed onthe paint surface, due to
• Exposure to sun / UV light• Degradation of the binder• Weathering of the paint• Insufficient mixing of the paint
• Grind and/or wash top layer of the paint• Recoat
Appearance
Caused by
Repair
Paint School22
BleedingBleeding
• Discolouration of a paint, particularly intopcoats
• Coloured ingredients in a previous coat or onthe substrate is dissolved by solvents in thesubsequent coat, e.g.
• Soluble pigments (Poor solvent resistance)• Tar, Bitumen, etc.• Surface contaminants (coloured)• Re-blasting and re-application
Appearance
Caused by
Repair
Note:Note: Bleeding may continue through additional coats unless source is removed
Paint School23
DelaminationDelamination(Adhesion failure)(Adhesion failure)
Appearance• Loss of adhesion:
– Intercoat delamination: Between coats– Substrate delamination : Between primer and substrate
Caused by• Primer not compatible with subsequent coat• Contamination of substrate or between coats• Recoating interval too long• Blooming / sweating
Repair• Remove loose paint layer or down to substrate• Recoat
Paint School24
Mud-crackingMud-cracking
Appearance• Cracks occurring during the drying process of the paint• Appearance of the surface of cracked mudCaused by• Particularly for inorganic Zinc applied at a too high film
thicknessRepair• Re-blast to Sa 2½ or grind off• Apply the inorganic Zinc
Jotun Paint School Course Handouts Page 47
9. AntifoulingAll surfaces exposed to seawater will be "attacked" by marine organisms. When theseorganisms attach and grow, they cause a significant increase in surface roughness. On a ship'shull, this results in greater friction resistance and hence increased fuel consumption. It istherefore extremely important to prevent marine fouling when assessing a ship's fueleconomy. The types of organisms and their growth rates vary with the temperature of theseawater, salinity and the light intensity in the sea. Plant organisms are normally diatoms orgreen/brown algae, whereas the most common animal organisms are Cirripedia (barnacles),bryozoa and hydroids.
The most common way of preventing the fouling of marine structures is to apply apreventative coating or antifouling as we often call it. This contains one or more toxins(biocides) which are normally sufficient to make the antifouling effective against mostorganisms.
Antifouling paint can be divided into three categories: conventional, long life and self-polishing antifouling paints.
1. Conventional antifouling paints – also known as "soluble matrix" antifouling paint, havebeen in use for many years. The main binder is resin, a natural product which dissolves veryslowly in seawater. The Resin is brittle but although these formulations contain variousadditives, this type of antifouling often takes the form of a very weak film and the paint canonly be applied in relatively low film thickness. The effective protection against foulingvaries from 12 to 18 months. 2. Long life antifouling paints are also known as "insoluble matrix". The binder is notcompletely insoluble in seawater. The active components (biocides) and resin are released butthe binder remains on the structure as a porous frame. The porous film left after the biocideshave been released forms a weak substrate for a new coat of paint. It is thereforerecommended that a sealer coat be applied at each dry docking to create a better substrate forthe new antifouling. One risk with this type of antifouling is that year after year, coat aftercoat, many layers of paint are built up. This build up of layers can cause the paint to breakaway from the surface or from earlier coats, which increases the roughness of the hull. Thiscondition is called "sandwich coating" and, after fouling, is the main cause of increasedroughness on a ship's hull. Long-term antifouling paints are effective for about 24 months.
3. Self-polishing antifouling paints – hydrating type are based on a mixture of water-soluble and water-sensitive binders. These react with seawater to form a soft layer whichdissolves relatively easily in water. This type of antifouling was first developed when the needarose for tin-free antifouling paints. The effective life is about 36 months. In today's market, conventional, long-term and self-polishing hydrating antifouling paints arelargely tin-free. 4. Self-polishing antifouling paints – hydrolysing type contain a binder which is initiallyinsoluble in seawater. When the paint film is exposed to seawater, a thin layer on the surfaceof the film absorbs water and a chemical reaction occurs between the binder and the water(hydrolysis). This is the main difference compared with other antifouling paints. The reactionproduct is water-soluble and will slowly dissolve or be washed away. Thus fresh, new
Jotun Paint School Course Handouts Page 48
antifouling paint is constantly being exposed. This results in a linear/predictable rate ofbiocide release which ensures a highly effective antifouling action. This type of antifouling isavailable both tin-free and with tin. Both variants can give effective protection for up to 60months.
One very important reason for using self-polishing antifouling paints is to avoid the"sandwich coating", which often occurs when using conventional or long-term antifoulingpaints. With a self-polishing antifouling paint, the surface will not become porous and it is notnormally necessary to use sealers. When a ship is in dock, the hull is rinsed with fresh waterto remove slime and other contamination, and the new antifouling paint is then applieddirectly onto the old paint film.
Self-polishing antifouling paints are often based on copper with tin and/or other biocides.Those based on tin are restricted in most countries due to the environmental effects in the seaand will be prohibited from use within a few years. Copper-based products are more"environmentally friendly".
Personal notes
Chapter: Antifoulings
Jotun Paint school Handouts Page 49
Paint School1
What is fouling ? What is fouling ? (1 of 2)(1 of 2)
Fouling is the settlement and growth ofmarine plants and animals on man-
made structures in the sea
Paint School2
What is fouling ? What is fouling ? (2 of 2)(2 of 2)
There is an estimated 4 - 5000 fouling speciesand these can be classified into:
➨➨ Microfouling– generally referred to as slime, a complex
viscous mixture of bacteria and microscopicorganisms
➨➨ Macrofouling– which includes animals and plants
Paint School3
What is theWhat is theconsequence of foulingconsequence of fouling
On a ship’s hullIncreased fuel consumptionIncreased fuel consumption
On a marine structureIncreased drag Increased drag Heavier load on the structure Heavier load on the structure Structural failuresStructural failures
Seawater pipe systems–– Increased corrosionIncreased corrosion–– Reduced pipe Reduced pipe diametres diametres Pump failures Pump failures
Paint School4
Why do ships needWhy do ships needanti-fouling systems?anti-fouling systems?
Fouling leads to an increase in fuel consumptionof up to 40%, due to the increase in drag resistance
A clean ship sails faster and with less energy
Fouling will eventually damage the primer system
Paint School5
Selection of AntifoulingsSelection of Antifoulings
• Legislation / Environment• Type of ship• Speed• Trade / Voyage factor• Dry-docking interval:
–Conventional antifoulings: 1 - 2 years–TBT-containing antifoulings
(tributyltin): 5 years–TBT-free, self polishing antifoulings: 3 years
Paint School6
Hull roughnessHull roughness
• Permanent roughness– welding seams, valve openings, bulging
plates etc.• Temporary roughness
– flaking, dry spray, cracking, sagging,fouling etc.
Roughness can be divided in two main groups
Chapter: Antifoulings
Jotun Paint school Handouts Page 50
Paint School7
Frictional resistance depends on:Frictional resistance depends on:
• The speed of the ship• The area of the underwater hull• The shape of the hull• The roughness of the hull
Hull roughness is the only one of these factors which can be varied to a significant degree
Paint School8
Antifoulings and hull economyAntifoulings and hull economy
Calculation example: Panamax vesselAntifouling
– 7,000 litres at a cost of $ 40,000 - $ 50,000➡ 10% saving represents $ 4,000 - $ 5,000
Fuel cost– 10,000 HP at $ 100 / ton, sailing 250 days a year➡ Would save 5% or $ 100,000 in the same period
➡➡ 20-25 times better return
Paint School9
Application faultsApplication faults
• Typical application faults that increase roughness:– Overspray– Sagging– Dry spray– Paint spatter
• Poor application has a greater ill effect on the dragof a hull than wear and tear
Paint School10
Antifouling Antifouling challengeschallenges
• Main threat on sidebottom is fouling
• Main threat on flatbottom is roughness
Paint School11
Development of AntifoulingsDevelopment of Antifoulings
Influencing factors the past thirty years:
➊ Demands from shipowners for better performance witheconomy
➋ Increased emphasis on surface roughness and hullperformance
➌ Increases in fuel oil prices over the period➍ Technological achievements by many antifouling
manufacturers➎ The trend to extend periods between dry-dockings➏ The increasing awareness of environmental issues
Paint School12
Main types ofMain types of antifoulings antifoulings
1. Conventional Antifouling
2. Long-life Antifouling
3. Selfpolishing Antifouling
Chapter: Antifoulings
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Paint School13
The composition of AntifoulingsThe composition of Antifoulings
• Binder• Biocide• Extenders• Pigments• Solvents• Additives
?
Paint School14
Conventional AntifoulingsConventional Antifoulings
• Soluble matrix paints• Rosin as a binder• Approximately 12 months protection• Binders dissolves in water and biocide is released• Often called: Tropic, Super Tropic etc.
NOTE:NOTE:Danger of cracking and flakingNeeds to be quickly immersed in water
Paint School15
Long-life Long-life AntifoulingAntifouling
• Insoluble matrix paints• Only biocides are released• Effective protection is up to 24 months• Leaves weak substrate for subsequent coat• Sealer coat normally required• Binder: CR, Vinyl (possible to add small
amount of colophonium)• Often called Sargasso etc.
Paint School16
Self polishing AntifoulingsSelf polishing Antifoulings
• Predictable performance• Extended dry docking period• Control of roughness and smoothing• No “sandwich coatings” problems• Fouling control due to linear biocide release• Lifetime directly proportioned with dry film
thickness
Paint School17
Selfpolishing AntifoulingSelfpolishing Antifouling with TBT with TBT
• Introduced in the 1970’s• Contains chemically bound organotin• Released by hydrolysis in seawater• In addition, biocides like cuprous oxide
(Cu2O) and organic boosters are used• The rest of the copolymer is water soluble
and is worn off, usually by friction• Reduce hull roughness• No sealer coat required for recoating
Paint School18
Self-polishing Self-polishing AntifoulingAntifouling - Tin free - Tin free
• Blend of water soluble and water sensitivebinders or hydrolysable binders.
• With respect to performance the early ‘ablative’antifoulings have been refined close to thosecontaining tin.
• Not identical to tin based antifouling inperformance yet.
Chapter: Antifoulings
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Paint School19
Rel
ease
rat
e (µ
g/cm
2 /
day)
40
30
30
10
1 2 3 Time, years
Conventional A/F
Long life A/F
Selfpolishing A/F
Comparison of release rate of biocide for different A/F-types
Release rate for Anti-Release rate for Anti-foulingsfoulings
Minimum release level for
fouling protection
Paint School20
Why is hydrolysis so important ?Why is hydrolysis so important ?
Because:• Linear erosion rate assures long term antifouling
property• No skeletal layers means good adhesion• Continual smoothing of the surface ensures good
fuel efficiency• Hard film maintains its good appearance
Paint School21
Rules and regulationsRules and regulations
• MEPC approved a draft assembly resolution inNovember 1998 agreeing that:
A complete prohibition on the presence of TBT anti-fouling systems on ship’s hulls to be in place by 1.1.2008
A complete prohibition on the presence of TBT anti-fouling systems on ship’s hulls to be in place by 1.1.2008
The application of all anti-fouling systems containing TBTshould be prohibited throughout the world by 1.1.2003
The application of all anti-fouling systems containing TBTshould be prohibited throughout the world by 1.1.2003
Paint School22
New tin-free technologyNew tin-free technology
SeaQuantum - Advanced tin-free anti-foulingSeaQuantum - Advanced tin-free anti-fouling
Meets the draft IMO regulations for 2003 and 2008Meets the draft IMO regulations for 2003 and 2008
With performance that exceeds what has gone beforeWith performance that exceeds what has gone before
Matches tin-containingMatches tin-containing selfpolishing selfpolishing performance performance
With a track record of success in With a track record of success in newbuilding newbuilding andanddrydockingdrydocking
Based on a unique hydrolysing Based on a unique hydrolysing silylsilyl polymer polymer
Paint School23
• Because linear polishing rateassures long term antifoulingproperty
• Because no skeleton layer meansgood adhesion
• Because continuous smootheningof the surface ensures good fuelefficiency
• Because hard film maintains itsgood appearance
New tin-free technologyNew tin-free technologyWhy is hydrolysis so important?Why is hydrolysis so important?
Newly appliedSteel hull
After exposure in the seaSteel hull
Paint School24
Anti-fouling for Aluminium hullsAnti-fouling for Aluminium hulls
Special requirements:• Must be free from Copper• Must perform at speeds up to 50 knots• Preferably selfpolishing
Can also be used on steel hulls:• When port calls are frequent• When service distances are short• For laid up ships
Jotun Paint School Course Handouts Page 53
10. Safety, Health and Environment (SHE)In recent years, awareness of SHE-related matters has increased. This is reflected inlegislation and by companies and individuals becoming involved in such matters. At the PaintSchool, we have decided to focus on health problems in connection with the surface treatmentof structures.
General guidelinesDuring the preparation and use of paint, it is important to be aware of the risks associated withthe activity. In brief:
• Follow current legislation from local and national authorities.• Read the safety data sheets for all products. Know the risks and how to protect yourself.• Obtain the necessary training in the use of the products and equipment to be used.• Use the necessary protective equipment to protect the respiratory system, eyes, skin and
hearing.• Inspect all areas where work will take place to reveal possible SHE faults.• Ensure correct storage and handling of products and associated thinners before, during and
after the work. The products should be collected in a specially allocated area.
SafetySafety aspects are particularly important in connection with the use of solvent-based paints.Solvents are flammable and in the right environment and under unfavourable conditions cancause both fire and explosion. Be aware that solvents are heavier than air and will sink downto areas which lie below the painting work.
In general, the following aspects should be checked in connection with painting work.
• Plan the work and co-ordinate this with other activities in the area.• Inspect the area where the work is to be performed. Shut off the areas affected. Remember
areas which are lower than that where the painting is to be performed.• Check the equipment to be used, including safety and protective equipment.• Closed rooms must be declared gas-free before work begins.• Take extra safety precautions when painting in tanks and confined areas: Adequate
ventilation, explosion-proof working lights and equipment, an assistant with a line andadequate breaks in fresh air.
HealthSurface treatment represents a health risk. The risk can however be reduced to a minimum ifthe operators and people in the vicinity of areas where such work is in progress proceed asfollows:
• Read the safety instructions and SHE documentation for the product (safety data sheet)• Follow the instructions given. In particular: use adequate approved protective equipment
e.g. fresh air masks, gloves, protective goggles and anti-static footwear/clothing.
The most serious health risks are associated with the following:
Jotun Paint School Course Handouts Page 54
Solvents• Irritation of the skin, eyes and respiratory organs• Can be absorbed through the skin. Degrease the skin. Can cause eczema• Negative effects on the liver, kidneys, respiratory organs, blood, central nervous system
and reproductive organs• Can cause headaches, dizziness and fatigue
Epoxy• Irritation of eyes and skin• Causes skin allergy• For sensitive persons: epoxy allergy can be life-long
Isocyanates• Irritation of eyes, skin and respiratory organs• Causes allergy to the skin and respiratory organs• For sensitive people: allergies can be life-long• At high temperature: toxic gases such as free isocyanates can be emitted
Heavy metals: Dust and vapoursMetals harmful to health are mainly: chromium (IV), lead, iron, cadmium, cobalt, copper, zincand nickel. The organs which can be affected (examples of symptoms/effects):• Respiratory organs (metal fever)• Skin (eczema)• Blood cells (anaemia)• Nervous system (fatigue)• Heart (irregular pulse)• Kidneys (reduced function)• Bone structure (accumulation)
DustDust is a factor which must be taken into account both during pre-treatment and sprayapplication. Dust is inhaled through the nose and mouth and can cause lung damage (dustdisease, silicosis) and irritation of the eyes. Dust on the skin can also cause irritationdepending on what the substance contains.
NoiseNoise is primarily linked with steelwork and preparation. Many tools produce noise levelsover 100 decibels. A lower limit for the use of ear protectors is often set at around 80decibels.
Personal notes
Chapter: SHE
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Paint School1
Many risks are involvedMany risks are involvedwhen working with paintswhen working with paints
Safety– Explosion and Fire
Health– Manufacturing and Surface treatment
Environment– Emission to air (VOC)– Emission to water (Maintenance)– Emission to soil (Waste handling)
Paint School2
Solvents are heavier than air
• A fire may start in lower areas or compartments• Ignorant personnel below can be affected
Safety hazard: SolventsSafety hazard: Solvents
Paint School3
Safety risk:Safety risk:High pressure equipmentHigh pressure equipment
Surface treatment involves equipment with very high pressures
Never point any high pressure unit at another person or at yourself !!
• Blast cleaning - Mixture of air and particles• Water Jetting - Water up to above 2500 Bar• Airless spray application - Paint
Paint School4
How can we reduce the possibilityHow can we reduce the possibilityfor accidents to happen ?for accidents to happen ?
• Read the Safety Data Sheet and follow thegiven precautions and advices
• Check the surrounding areas for nearbyactivities, particularly welding, machining etc.(remember lower levels)
• Ensure proper ventilation and check thedirection where solvents may move
• Always use approved and sufficient personalprotection equipment of approved type
Paint School5
How flammable is a paint ?How flammable is a paint ?
The “Flash point”“Flash point” tells how flammable a Paint is.
The flash point is the lowest temperatureat which the fumes from the solvents
ignite or explode
Classification:Classification:� Extremely flammable: Flash point below 0 °C� Highly flammable: Flash point between 0 and 21°C� Flammable: Flash point between 21 and 55 °C
This information can be found in the Safety Data SheetPaint School6
Precautions when paintingPrecautions when paintingin confined spaces.in confined spaces.
• Ensure good ventilation• Exhaust points for fumes / solvents must be close
to the bottom• Start application from the bottom and up• Always use non-sparking tools• Use antistatic clothing with hood• Use masks with air supply• Use boots and gloves• Safety lines• Sufficient rest periods
Never smokeor use naked flames !
Chapter: SHE
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Paint School7
SymbolsSymbolsFire and explosion hazardsFire and explosion hazards
These symbols can be found inSafety Data Sheets and on the paint tin label
Explosive Oxidizing Extremelyflammable
Highly flammable
E O F+ F
Paint School8
SymbolsSymbolsHealth hazardsHealth hazards
These symbols can be found inSafety Data Sheets and on the paint tin label
Very Toxic Toxic Corrosive Harmful Irritant
T+ T C Xn Xi
Paint School9
Types of information to be found inTypes of information to be found in the safety data sheet (16 points). the safety data sheet (16 points).
1. Identification of the company2. Composition and ingredients3. Hazard identification4. First aid measure5. Fire fighting Measures6. Accidental release measures7. Handling and storage8. Exposure control and personal
protection
9. Physical and chemical properties10. Stability and reactivity11. Toxicological information12. Ecological information13. Disposal considerations14. Transport information15. Regulatory information16. Other information
Paint School10
Evaporation of solvents duringEvaporation of solvents duringapplication of an objectapplication of an object
Area: 20.000 m² Dry Film thickness: 300 microns
0
1000
2000
3000
4000
5000
Mastic Tar Epoxy Alkyd CR82 % 65 % 50 % 40 %
Litres of Solvents
Vol. % Solids
Paint School11
General precautions forGeneral precautions forsurface treatment surface treatment (1 of 3)(1 of 3)
Before the work starts• Do not start the work without proper training or experience• Know all safety routines and where to find
necessary equipment if an accident should occur• Read and understand all Safety and Technical Data Sheets• Know all the hazards involved (R phrases)• Know all protective measures requires (S phrases)• Availability of appropriate, personal protection equipment• Evaluate the work place regarding - Other nearby activities, warning signs,
mixing station, first aid kits, ventilation, housekeepingPaint School12
During work• Always use appropriate, approved
personal protection equipment• Use the tools and equipment correctly to avoid
injuries to others or to yourself• Keep all containers / tins closed• The work can be exhausting: Take sufficient rests• Keep the work place tidy during the work
General precautions forGeneral precautions forsurface treatment surface treatment (2 of 3)(2 of 3)
Chapter: SHE
Jotun Paint school Handouts Page 57
Paint School13
After work• Close all Containers / tins• Clean the equipment properly• Store unused paint and thinners safely (Paint store)• Throw waste in designated containers. (Hazardous
waste)• Clean the personal protection equipment
and store it properly to avoid contamination• Clean yourself with water and cleaning cream
General precautions forGeneral precautions forsurface treatment surface treatment (3 of 3)(3 of 3)
Paint School14
Filter typesFilter types
DustP1: Lowest degree of protectionP2: Medium degree of protectionP3: Highest degree of protection
Gas from organic solventsA1 Lowest degree of protectionA2 Medium degree of protectionA3 Highest degree of protection Other types might be
required for productsclassified as corrosive.
Paint School15
Health Health hazardshazardswhen using paintswhen using paints..
BindersBinders• Skin contact.• Particularly Epoxy, Amines and Isocyanates may
cause skin irritation and Allergic reactions
Other constituents:Other constituents:• Tar, Heavy metals
• By inhalation• Skin contact• Ingestion
Solvents: May enter the body in three ways:
Paint School16
Health Health hazardshazards from fromsolventsolvent exposure exposure
Acute effects• Headache• Abnormal tiredness• Dizziness• Nausea
Long term effects• Irritability • Loss of memory• Organ damages
(kidneys, liver, CNS)• Reduced reaction ability• Reduced evaluation ability
Skin irritations• Eczema• Dry and cracked skin
Paint School17
Health hazard:Health hazard:inhalation of solventsinhalation of solvents
The most dangerous hazard• Solvents will be transported by the blood stream to internal
organs of the body.• Amount absorbed and the effect on the body will depend
on: Type of solvent, period of exposure, concentration andwork load.
• May cause damage to: Central nervous system, respiratorysystem, liver, kidneys and reproductive systems,
Protective measures:Proper ventilation.
Use approved, protective mask
Paint School18
Health hazard:Health hazard:Skin contact with solventsSkin contact with solvents
The most frequently occurring health effects• Causes:
- Reddening - Swelling - Drying and cracking of skin - Absorption through intact skin: Some, like Xylene - Absorption through damaged skin: Several, like White Spirit
Protective measures: Avoid direct contact
Protective clothes, gloves and boots
Chapter: SHE
Jotun Paint school Handouts Page 58
Paint School19
Health Health hazards whenhazards whenworking with working with EpoxiesEpoxies..
Hazards :� Eczema and allergic reactions on the skin� Liquid Epoxies with low molecular weigths (below 700) are most likely to give an allergic reaction� An allergic reaction to Epoxy is irreversible.� Hyper-sensitive persons must stay away from epoxies.
Protective measures� Protective clothes covering the whole body and gloves� Proper cleaning with water, soap and cleaning cream� Use disposable overalls
Paint School20
Health Health hazards whenhazards whenworking withworking with tartar containing paints containing paints..
Hazards� The main hazard with tar containing paints is the risk for
developing cancer, especially when exposed to strong sunlight� Long term exposure to vapours may damage internal organs,
cause heritable genetic defects and birth defects� Short term exposure to fume and vapours may cause irritation
to nose, throat and eyes� Splashes to skin causes irritationProtective measures� Protective mask to avoid breathing vapours� Protective clothes covering the whole body and gloves
Paint School21
Health Health hazards when workinghazards when workingwith paints containing with paints containing IsocyanatesIsocyanates..� The monomer is more volatile than the pre-polymer and is
therefore more dangerous� Isocyanates are found in Polyurethane paintsHazards� Irritation of eyes skin and airways� Sensitization by inhalation and skin contact� AsthmaProtective measures� Protective mask to avoid breathing of vapours� Protective clothes covering the whole body, boots and gloves
Paint School22
Some times used in pigments, additives or driers.Hazards (Metal fumes,dust from hot work)� Zinc. Dust and fumes: Zinc fever, chills, coughing, irritation� Copper. Fumes: Metal fever and chills� Lead. Dust and fumes. Damage blood cells, Anemi, skeleton,
reduced fertility and central nervous system� Chromium. Dust and fumes: Sensitisation, cancer� Nickel / Cobalt. SensitisationGeneral Protective measures� Protective mask to avoid breathing of vapours� Protective clothes covering the whole body, boots and gloves
Health Health hazards when workinghazards when workingwith paints containingwith paints containing heavyheavy metals metals..
Paint School23
• Antifoulings are generally looked upon as Toxic• Some antifoulings contain Tin• Tin may cause irritation to skin and eyes the central
nervous system and effect the immune system
General Protective measures� Protective mask to avoid breathing of
spray mist / droplets� Protective clothes covering the whole body,
boots and gloves
Health Health hazards when workinghazards when workingwith with antifoulingsantifoulings..
Paint School24
How dangerous is aHow dangerous is achemical or a paint ?chemical or a paint ?
Different persons will respond differentlyIn general the hazard will depend on:
The concentrationand risk of exposure
The toxicity and amount
of the compound
The contact period with the chemical
Jotun Paint School Course Handouts Page 59
11. Corrosion
What is corrosion?
To give materials satisfactory protection against corrosion, it is important to understand whatcorrosion is. Only once we know when, how and why a material corrodes (rusts) can wespecify the right material and give the material a cost-effective protection.
Corrosion is defined as "a material’s reaction with the surrounding environment during theformation of corrosion products". From this definition, it is clear that it is not enough toknow the properties of the material, we also need knowledge of the exposure environment.This means that we need to know how corrosive the environment surrounding the material is.To illustrate the different material properties, consider the following example: gold will notcorrode in seawater and therefore we call this an inert material in this environment. Zinchowever is far from inert. Similarly a particular material will have a totally different longevityin two different environments: unprotected steel corrodes quickly in seawater but will bealmost everlasting in a dry indoor atmosphere.
The corrosion process
The corrosion process is caused by the supply of energy to metals when they are producedand processed. This is an undesirable energy state and the metal will try to return to its naturalcondition. This can involve the material dissolving into metal ions and electrons. For such areaction to occur, the metal must form part of a corrosion cell. A corrosion cell consists oftwo different materials connected together via a conductive electrolyte and a metal conductor.A conductor can be another conductive material or it can be a direct contact between the twometals. The conductive electrolyte can for example be seawater or condensation with someform of contamination or salts which make the condensation conductive.
If we regard the corrosion process as an electrical circuit, it is easy see that we can stop or atleast reduce the corrosion by either breaking the electrical circuit or by increasing theresistance in the circuit. This is the principle behind the use of many paints as corrosionprotection. When paint is applied to the metal, we apply an insulating layer and it becomesmore difficult for the conductive ions in the electrolyte to reach the surface of the metal. Theohmic resistance in the circuit increases. Another method is to change the surroundingenvironment. We can for example prevent condensation forming by changing the temperatureof the metal or by ensuring better ventilation.
Corrosion types
There are many different forms of corrosion. Although we will not discuss all of them, weshould briefly mention the two most common types on steel structures: galvanic corrosion,general corrosion and crevice corrosion.
Galvanic corrosion occurs when two different alloys are connected together in an electricalcircuit, as described for corrosion cells. In such a circuit, it is always the most negative metalwhich corrodes. This metal is called the base metal or the anode in the circuit. The noble
Jotun Paint School Course Handouts Page 60
metal or cathode will actually acquire a certain degree of protection (see cathodic protection).Typical examples of galvanic corrosion are aluminium which corrodes when connected tosteel or a cast iron valve which is connected to an aluminium-brass pipe.
In principle, general corrosion is very similar to galvanic corrosion except that the corrosionprocess occurs on one metal only. The galvanic cell occurs when either various alloy elementsor contaminants are present in the metal or the metal surface is uneven. The corrosion willoccur on the most base elements on the alloy surface.
Crevice corrosion is a type of corrosion which is mostly found on passive materials such asstainless steels. The attack takes place in narrow gaps or crevices. Critical crevices forinitiation of corrosion are between plates, pores in welds, between gasket and flange in pipesystems, under various types of settlements (marine mud) and contamination (paint splashes).The reason for the attacks is that the environment inside the crevice is different from theenvironment outside. A corrosion cell will be formed between the two areas. A ondition thatwill increase the risk of attack even furter is the presens of aggressive ions such as chloridesfound in seawater. Once initiated the crevice corrosion attack may propagate at a very highspeed and cause rust penetration within a surprisingly short period of time.
Personal notes
Chapter: Corrosion
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Paint School1
Definition of CorrosionDefinition of Corrosion
Corrosion is a reaction between
Materialand
Surrounding environment
under formation of corrosion products
Paint School2
Production andProduction anddegradation of steeldegradation of steel
Plates, pipes,profiles, etc.
Energy
Manufac
turing
Water /humidity
Oxygen
Raw materialIron ore Rust
Reaction between the material and the surrounding environment takes place
The presence of water / humidity and Oxygen is a pre-requisite for corrosion of steel
Paint School3
How is rust formed ?How is rust formed ?
Painted surfaceexposed to humidity
The water molecules penetrate the paintDue to osmotic forces blisters are formed
The blisters break andcorrosion is initiated
Paint School4
Freely corroding steelFreely corroding steel
Electrolyte (Water or soil)
Steel
Cathode CathodeAnode
Paint
Paint School5
Pre-requisites for corrosionPre-requisites for corrosion
• A Cathode:The noble metal / alloy (or part of metal)
• An Anode:The less noble metal / alloy
• An electrical connection between the two metals.Conducting electrical current (by electrons)
• An electrolyte:Conducting electrical current (by ions)
A galvanic cell consists of:
Paint School6
AA galvanic cell galvanic cell
In seawater, a calcareous deposit is formed on the steel surface
2 e
Zn = Zn + 2 e
Cathode:Steel Anode:
ZincO2
½ O2 + H2 O + 2e = 2OH
2+ -
- -
-
-
Chapter: Corrosion
Jotun Paint school Handouts Page 62
Paint School7
Aluminium Zinc Steel
Protective Iron oxide
In a strong alcaline environment Aluminium and Zinc will corrode rapidly, while steel will be passive
Corrosion speed differ whenCorrosion speed differ whenexposed to the same environmentexposed to the same environment
pH > 10
Paint School8
Galvanic potentials in seawaterGalvanic potentials in seawater
Paint School9
Steel inSteel in Seawater SeawaterPotentialPotential versus versus Zinc Zinc & Ag/Ag & Ag/Ag ClCl ref. ref. electrodeselectrodes
Rapid corrosion
General corrosion
Some corrosion
100% Cathodic protection
Overprotection
Possible coating damage
Increasing polarisation
Ag / Ag Cl Zinc
+ 0.50
- 0.25
+ 0.0
+ 0.25
- 0.55
- 1.30
-1.05
- 0.80
Potentials in volt
- 0.60
- 1.35
-1.10
- 0.85
Cu / CuSO4
Paint School10
How to measure the corrosionHow to measure the corrosionpotential of a structurepotential of a structure
+ -
Reference electrode
Volt meter
Structure
Sea water
Paint School11
Elements influencing theElements influencing thecorrosion speed of metalscorrosion speed of metals
• Temperature• Salinity• Oxygen content• Water velocity• Acidity (See below)• Type of electrolyte ( e.g. cargo or chemicals)• Content of contaminants / pollution that
promotes corrosion• Micro-organisms.
Submerged materials
Paint School12
Neutral
Acidic
Alcaline
pH-scalepH-scale
Chapter: Corrosion
Jotun Paint school Handouts Page 63
Paint School13
ParametresParametres influencing the corrosion influencing the corrosionspeed. Atmospheric corrosionspeed. Atmospheric corrosion
• Humidity• Temperature• Concentration of salts• Amount of air pollution,
including acid rain, soot and dust particles
Paint School14
Apart from using paint and CP:Apart from using paint and CP:How to protect against corrosion ?How to protect against corrosion ?
• Good design• Avoid corrosion traps• Improved accessibility - maintenance• Proper materials selection• Insulate between dissimilar materials• Change the surrounding environment• Remove water / humidity• Apply metallic coatings• Use corrosion inhibitors (closed systems)
Corrosion protection can be achieved in many waysCorrosion protection can be achieved in many ways
Paint School15
Avoid stagnant water atAvoid stagnant water atbottoms of tanks and containersbottoms of tanks and containers
Unfortunate Better Best solutionx
x x
Paint School16
CorrosionCorrosionProperties of the materialsProperties of the materials
• All materials have their strong sides• But, they also have their weak points
Knowledge is required for selecting the correct material for a given application
Paint School17
Most frequently occurringMost frequently occurringtypes of corrosiontypes of corrosion
On carbon steel• Uniform corrosion• Uneven corrosion (deep pits)• Galvanic corrosion• Stress corrosion cracking
Paint School18
Most frequently occurringMost frequently occurringtypes of corrosiontypes of corrosion
Stainless steels• Crevice corrosion• Pitting corrosion• Stress corrosion cracking
Titanium• Hydrogen embrittlement
• Fatigue
Aluminium• Pitting corrosion• Galvanic corrosion
Copper based alloys• Erosion corrosion
Chapter: Corrosion
Jotun Paint school Handouts Page 64
Paint School19
Steel with mill scaleSteel with mill scale
Outdoor exposure• The mill scale cracks• Corrosion will develop on the steelMill scale is more noble than steel
Mill scale Corrosion
Steel Steel
Paint School20
Crevice corrosion occurs underCrevice corrosion occurs underpaint spillage or platespaint spillage or plates
StainlessStainless Steel Steel
PaintPlate
Corroded areas
Ingress of seawaterSeawater
Crevice corrosion occurs in narrow gaps where the oxygen concentration is lower than
on the freely exposed part of the material
Paint School21
Galvanic corrosion is to a large extentGalvanic corrosion is to a large extentdetermined by the conductivity of the electrolytedetermined by the conductivity of the electrolyte
Anode Cathode
Corroded area
The corrosion attack decreases with increasing distance from the cathode due to an increased ohmic resistance
Electrolyte (Seawater)
Paint School22
Pitting corrosionPitting corrosion
• Pitting corrosion is a localised attack on a material normally protected by a passive film• The passive film may be destroyed mechanically or by aggressive ions in an electrolyte• Severe corrosion may take place beneath the passive layer
Seen from above Cross section
Stainless steel
Passive layerPitting corrosion
Paint School23
Corrosion fatigueCorrosion fatigue
No. of dynamic cycles
Load
No failure above line
Fatigue only
Corrosion fatigue
Corrosion Fatigue is a combined effect of an aggressive environment and dynamic loads on a structure
Paint School24
Stray current corrosionStray current corrosion
- +Welding transformer
Quay
Corrosion
Stray current
To earth
Pontoon
Seawater
Welding on board
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12. Cathodic Protection
Basic conditions
Cathodic protection (CP) is one of the most common forms of corrosion protection. Tounderstand how this method works, you need to be familiar with a few basic facts. The first isthe mechanism behind the corrosion process (see the section "Corrosion"). Remember that thevery occurrence of the corrosion process means that when a metal corrodes (rusts), the metalbreaks down into ions and electrons are released.
It is also necessary to understand what an electrochemical cell (corrosion cell) is. This is aconductive circuit which consists of a noble metal (cathode) and a base metal (anode) inmetallic contact with each other. In addition, the metals must be in contact with each other viaa conductive electrolyte (for example seawater). In such a circuit, it is always the anode whichcorrodes, while the cathode will be protected.
Which metal will corrode in a cell ?
When two metals are connected together, we can predict which will corrode and which willbe protected. This is due to the electrochemical voltage level of the metal, or corrosionpotential. The potential for a metal can be measured by putting the metal in seawater andmeasuring the voltage between the metal and a reference electrode. When we have measuredthe potential of several metals, we can classify them. The most noble is placed at the top ofthe list and the most base at the bottom. This classification is called the ‘Galvanic series’. In aconnection between two metals, the most negative metal will be the anode whilst the metalhigher up in the table will be the cathode.
Principle of cathodic protection
Cathodic protection is based on preventing a metal from dissolving. By ensuring thatelectrons cannot be released from the metal we want to protect, the corrosion can be limited orstopped. This is done by connecting a more negatively charged metal (e.g. aluminium) to themetal we want to protect (e.g. steel). Aluminium will release electrons more readily and willhave enough power to propel the electrons into the steel and thus prevent dissolution.Aluminium is therefore the anode and will corrode instead of the steel. The aluminium issacrificed, hence the name sacrificial anode.
When the negatively charged electrons enter the steel, the steel will of course have a morenegative potential than it has in its free state. It is this change in potential which protects thesteel. To ensure protection, the steel must fall below a certain negative potential level. Thislevel is called the protection potential and is specified as a design criterion. The protectionpotential is normally of the order of -800 mV relative to a silver/silver chloride referenceelectrode.
An anode can only release a certain number of electrons before it is consumed. To ensure thatthe anodes work as long as necessary, we must calculate how many anodes are required.These calculations are called ‘designing a cathodic protection system’. A design requires
Jotun Paint School Course Handouts Page 66
knowledge of some important parameters. The most important ones are the area to beprotected, the type of material to be protected, the type of anode to be used, the lifetime of thesystem and the area of the structure which has been painted. A painted structure requiresfewer anodes than an unpainted one.
Finally: cathodic protection can be achieved by a forced voltage system. These systemssupply DC current to the steel in the same way as anodes.
Personal notes
Chapter: Cathodic Protection
Jotun Paint School Handouts Page 67
Paint School1
Corrosion of a metal or alloyCorrosion of a metal or alloy
• Corrosion is a reaction between the metal and the surroundingenvironment
• The corrosion rate depends on the properties of the metal andthe corrosivity of the environment.
• Corrosion is dissolution of the metal, among other thingsinvolving the release of electrons:
2+Fe →→→→ Fe + 2e
Paint School2
How to protect a structureHow to protect a structure
Corrosion Protection can be achieved by :• Sacrificial Anode Cathodic Protection System• Impressed Current Cathodic Protection System
Both systems supply electrons to the structure.The structure will become more negative and metal
dissolution will be prevented
Paint School3
• Zinc– Noranode– Coral Z
• Aluminium– Coral A– Coral A high grade
• Magnesium
Type ofType of sacrificial anodessacrificial anodes
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MarineMarineObjectsObjects to be to be protectedprotected::
• Ships• FPSO / FSU• Mobile rigs• Floating dry-docks• Barges
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Offshore and Offshore and industryindustry (Norwegian (Norwegian sectorsector).).ObjectsObjects to be to be protectedprotected::
• Offshore platforms– Fixed/floating– Concrete/steel
• Subsea installations– Templates/manifolds/
modules.• Subsea pipelines
• Harbour facilities– Piles– Sheet piles
• Buried tanks andpipelines (onshore)
• Above ground storagetanks
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TheThe principle principle of cathodic of cathodic protection protection..potentials vspotentials vs. different reference. different reference electrodes electrodes
+ 500
+400
+300
+200
+100
0
- 600
- 700
- 800
- 900
- 1000
- 1100
Freely corroding steel
Mixed potential
Freely corroding Zinc
mVZn
Cu /
CuSO4
Chapter: Cathodic Protection
Jotun Paint School Handouts Page 68
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Cathodic Cathodic ProtectionProtectionSteel Steel protected protected by a by a sacrificialsacrificial anode anode
Electrolyte (Water or soil)
Cathode Anode
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Rapid corrosion
General corrosion
Some corrosion
100% Cathodic protection
Overprotection
Possible coating damage
Corrosion potentialsCorrosion potentials in in seawaterseawaterZincZinc, Ag/Ag , Ag/Ag ClCl and and CuCu/CuSO/CuSO4 R4 Reference eference electrodeselectrodes
Ag / Ag Cl Zinc
+ 0.50
- 0.25
+ 0.0
+ 0.25
- 0.55
- 1.30
-1.05
- 0.80
Potentials in volt
- 0.60
- 1.35
-1.10
- 0.85
Cu / CuSO4
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ReductionReduction of of corrosion corrosion rate of steel by rate of steel bycathodiccathodic protection protection.. Moving seawater Moving seawater
Corrosion rate(per cent)
Free corrosion100
50
10
Full cathodic protection
-600 -650 -700 -750 - 800 -850+500 +450 +400 +350 +300 +250
mVCu / CuSO4Zn
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MarineMarineDesign criteriaDesign criteria
• Design lifetime• Coating system and condition• Current density (Coating type and
damages)• Electrolytic resistivity• Environmental conditions / impacts• Ballasting period.
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ProtectiveProtectiveDesign criteriaDesign criteria
• Design lifetime• Coating system and condition• Protection potential• Anode capacity• Electrolyte resistivity• Environmental conditions/impacts
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Current density requirementCurrent density requirementdependsdepends on: on:
A. Environmental parameters• Sea water composition and
salinity• Sea water temperature• Resistivity of sea water• Sea water flow velocity• Other factors, marine growth
B. Steel surface• Painted / not painted• Steel temperature• Coating system, if any• Condition of coating
system
Chapter: Cathodic Protection
Jotun Paint School Handouts Page 69
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Sacrificial anode material selectionSacrificial anode material selection
Main TypesMain Types• Zinc• Aluminium• Magnesium
Anode material selectionAnode material selection• Chemical composition• Electrochemical
performance- Anode potential- Stable current- Consumption
• Anode corrosion pattern• Price• Class requirements
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ComparisonComparison of cathodic of cathodic protection protection systems systemsgeneralgeneral advantagesadvantages::
Sacrificial anode systems• Simple, reliable and free
from in-service operatorsurveillance
• System installation issimple
• Low installation cost for short term protection
Impressed current systems• Flexibility under widely
varying operating conditions• Weight advantage for large
capacity, long life systems• Low friction (reduced sea
water drag)• Low life cycle cost (LCC)
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ComparisonComparison of cathodic of cathodic protection protectionsystems general systems general limitationslimitations
Sacrificial anode systems• Large weight for large
capacity, long life systems.
• Response to varyingoperating conditions islimited.
• Hydrodynamic loadings canbe high (Seawater drag)
Impressed current systems• Relative complexity of
system demands high levelof design expertise.
• In-service operatorsurveillance required.
• Vulnerable to componentfailure or loss of power.
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Why chooseWhy choose an ICCP system on hull an ICCP system on hull
• Smooth hull, no drag• Flexible dry-docking intervals• Low cost for long term operation• Long lifetime, minimum of maintenance• No welding required at dry docking• No risk of damaging internal Paint systems• Fully automatic corrosion protection
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Why chooseWhy choose a SACP system on hull a SACP system on hull
• Simple installation
• Maintenance free between dry docking
• Low cost for short term operation
• World-wide availability
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ShipShip hull: hull: Current density Current density at atdifferentdifferent paint paint damage damage
Current density, mA/m²20 40 60 80 100 120 140 160 180
100
80
60
40
20
0
Paint damage, %
Anodes ICCP
Chapter: Cathodic Protection
Jotun Paint School Handouts Page 70
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PrinciplePrinciple : : Effect Effect of of using using CP CPCorrosion Curves depend on - Coating condition - CP-design
Coating breakdown
CP installed
CP and coating at newbuilding
Time
Corrosion
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Corrosion in broken blisterCorrosion in broken blisterPassivation Passivation by CPby CP
Paint
Steel
Rust
Without Cathodic Protection
Paint
Steel
With Cathodic ProtectionAnodeAnode current
Seawater
Seawater
Calcareous layer
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ShipsShips hull: hull: Current density Current density as asfunctionfunction of coating of coating breakdown breakdown
Coating breakdown Current density 2 - 5 % 10 mA/m2
5-10 % 15 mA/m2
10-15 % 20 mA/m2
15-20 % 30 mA/m2
20-25 % 40 mA/m2
25-30 % 50 mA/m2
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Sacrificial anode systemSacrificial anode system
➊ Aluminium alloy anodes➋ Zinc alloy anodes (technically equal)
Aluminium is recommended prior toAluminium is recommended prior toZinc because:Zinc because:
☛ Aluminium anode weight is approx. 1/3 of Zinc☛ Total price for equal protection: Al. anodes
approx 1/2 of Zinc anodes☛ Lower installation costs due to weight difference
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Cathodic protectionCathodic protection❶ ICCP - Impressed Current❷ SACP - Sacrificial Anodes❸ EAF - Electrolytic Antifouling System for
seawater systems (CUPROBAN)❹ Slip ring arrangement for propeller shaft
Coatings and Cathodic ProtectionCoatings and Cathodic Protection
➡➡ The Single Source SolutionThe Single Source Solution
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Location of Pitguard anodesLocation of Pitguard anodes
Web frame
Web frame
Tank bottom
SeawaterAnode
Waterlevel