PSPC Training Material 3

IMO Performance Standard for Protective Coating and IACS Common Structural Rules

2nd Day Training

For the benefit of business and people

2BV Internal use only -

1 > Terms and definitions

2 > Corrosion basis

3 > Protective Coatings

4 > Coating Process

SUMMARY

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> Terms and definitions

1


Abrasive: the agent used for abrasive blast cleaning; for example, garnet, grit, shot etc.

Adhesion: The bonding strength; the attraction of a coating to the substrate.

Airless Spraying: An application method by which the paint is forced to a great pressure (up to 350 kg/sq. cm.) and is atomized by forcing it through a tiny nozzle.

Ambient temperature: The room temperature or temperature of surroundings.

Blast cleaning: Cleaning with propelled abrasive.

surface cleanliness : One free of contamination (including non-visible contamination such as soluble salts).

Coating system: A number of coats separately applied, in a predetermined order, at suitable intervals to allow for drying and curing, resulting in a completed job.

Curing Time: Time required by a coating to reach its complete properties and mechanical characteristic

Dew point is the temperature at which air is saturated with moisture.

DFT is Dry Film Thickness.

Dust is loose particle matter present on a surface prepared for painting, arising from blast-cleaning or other surface preparation processes, or resulting from the action of the environment.

Terms and definitionTerms and definition1


Edge grinding is the treatment of edge before secondary surface preparation.

Epoxy based: Film formers based on generic resins (binders) cross linked by amines,

polyamides or isocyanates.

Film thickness: The thickness of a coating layer or a multilayer coating system. Minimum and maximum values are the only relevant numbers when dealing with corrosion protection.

Humidity: Measure of moisture content; relative humidity is the ratio of the quantity of water vapour in the air to the greatest amount possible at the given temperature. Saturated air is said to have a humidity of 100%.

Material Safety Data Sheet: Document published by paint manufacturer in which components of the paints and all the safety requirements are given.

Primer: General term used to define the first coat of a paint system applied to provide adhesion and/or corrosion protection.

Profile depth: Average distance between tops of peaks and bottom of valleys on the surface.

Power Tool Preparation: Surface preparation method carried out by mechanical tools,

pneumatic or electric such as abrasive discs, wire brush, sandpaper etc.

Terms and definitionTerms and definition1


Terms and definitionTerms and definition

Recoat time: Time interval required between application of successive coats.

Shop-primer is the prefabrication primer coating applied to steel plates, often in automatic plants (and before the first coat of a coating system).

Stripe coating is painting of edges, welds, hard to reach areas, etc., to ensure good paint adhesion and proper paint thickness in critical areas.

Thinners: Volatile organic liquids for reducing viscosity; diluents.

Target useful life is the target value, in years, of the durability for which the coating system is designed.

Technical Data Sheet (TDS) is paint manufactures’ Product Data Sheet which contains detailed technical instruction and information relevant to the coating and its application.

Touch-up: Operation of repair of spot damage coated surface.

Two-Pack Paints: Paints stored in two separate containers and that have to be mixed in the correct proportion before application.

Wet Film Thickness: The thickness of paint film just applied and before evaporation of the volatile part.

Zinc silicate: Inorganic zinc coating.


Corrosion basis

•Definition and causes•Factors influencing the corrosion rate

2


Corrosion and coating Corrosion and coating

2-1 Definitions and causes

Steel Corrosion is the deterioration of the steel caused by its interaction with the environment

The Metal tend to return to a more stable thermodynamic state: iron oxide (rust) for steel

The Standard Electrode Potential* E0 measure the difference of potential at the equilibrium state between the metal and the electrolyte* :

The more E0 is negative the more the metal is electronegative (i.e. release electrons) and corrode easily

*E0 is calculated compared to the Hydrogen electrode

Basic Knowledge 2


- +

4 Electrolyte

Ions Migration

2-1 Definitions and causes

Four essential elements must be present to make the corrosion process likely to occur:

2

Metal oxidation (i.e. corrosion)Fe Fe++ + 2e-

Anode+

1

Reduction of Ions or oxygen:O2 + 2H2O + 4e- 4OH-

Cathode2

Electron Migration

3 Metallic Pathway or external conductor

ACME

Basic Knowledge Corrosion and coating Corrosion and coating


- +

4 Electrolyte

Ions Migration

2

Anode+

1Cathode2

Electron Migration


ACME

Rust

2-2 Factors influencing corrosion rate

[NaCl]



2-2 Factors influencing corrosion rateThe principal factors influencing corrosion rate are:

Electrolyte salinity [NaCl]: A high level of salinity (ex. 3.5% for seawater) increase electrolyte conductivity and so promotes corrosion and localised attacks. Chlorides produce breakings in the protective oxide films and so reduce metal corrosion resistance.

[NaCl] (g/L)

Corrosion rate

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2 Basic Knowledge Corrosion and coating Corrosion and coating


- +

4 Electrolyte

Ions Migration

2

Anode+

1Cathode2

Electron Migration


ACME

Rust


[O2]




2

The principal factors influencing corrosion rate are:

Electrolyte salinity [NaCl]

Oxygen concentration [O2]: A increase in [O2] causes a rise in corrosion rates.

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Corrosion rate

(Mils/yr)

[O2] (Parts per Billion)




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The principal factors influencing corrosion rate are:

Electrolyte salinity [NaCl]

Oxygen concentration [O2]

Electrolyte temperature T: Generally corrosion increase with temperature.

Bacteria: Bacteria present in seawater can cause local changes in corrosive conditions, and are therefore baneful for most metals.



2

Difference in potential E0: Particularly for galvanic corrosion when two metals or alloys are electrically in contact in a corrosive environment.

Relative surface areas of anodic and cathodic zones

Distance between anode and cathode



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Protective Coatings

•Definition and main components

•Coating families- a brief overview

•Concept of a coating system3


Protective CoatingProtective Coating3

3-1 Definitions and main components

Electron MigrationCathode Anode

O2 H2O Ions

Suitable Protective Coatings are used to prevent or retard corrosion in ballast tanks :

They act as a physical barrier that reduces corrosion rate

Protective coatingLow permeability

(Controlled Thickness and suitable formulation)

Good Adhesion with Substrate

Basic Knowledge


Protective Coating Protective Coating3


Conventional coatings have two major components :

• Pigment

• Vehicle

Basic Knowledge




Pigments are discrete particulate solids used to provide specific:

• protective

• or decorative properties (color, opacity and gloss)

to the coating.

They are Organic / Inorganic chemical products.

Basic Knowledge




Decorative Pigments:

• iron oxide (yellow, red etc.),

• titan oxide(white),

• candium compounds(red and yellow).

Basic Knowledge


Protective Coating Protective Coating3


Fillers are organic/inorganic particulates which allow the paint to be applied in thick layers, improve coating impermeability, adjust rheologic, gloss and mechanical properties, reduce cost formulation. (Silicium oxide, calcium carbonate, aluminum silicate, talc)

Main coating properties are controlled by the Pigment Volume Concentration (PVC).

Basic Knowledge




Vehicle is the liquid part of the coating. It consists of the binder, solvent and any liquid additives.

Binders (Resins) are part of nonvolatile film-forming components. It provide internal cohesion and flexibility and adhesion with substrate and gives the chemical resistance:

Solvents

Long Hydrocarbonate

chains

(binder)

Vehicle Scheme

Basic Knowledge




Solvents are volatile components. They may be classified as:

• Primary solvent (active): dissolves the resin to form a liquid solution

• Latent solvent: often used together with the primary solvent (easiness of application, evaporation rate control, enhance film properties)

• Diluents are used with active solvents to dilute the coating. In some cases diluents may improve smoothness and toughness of the film

Generally, paint formulators use a mixture of solvents to optimize the binder solubilisation, evaporation, viscosity etc.

The main use volatiles compounds are : white spirit, Xylen, Toluen, Methyl ethyl ketone (MEK), Metyl isobutyl ketone (MiBK).

Basic Knowledge


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The two major characteristics of solvents, which influence their use are:

• Solvency power: their ability to dissolve other chemical compounds

• Volatility: their ability to quit the coating (it governs the evaporation rate)

Solvent safety is concerned with two types of hazards:

• Fire hazards: Flash Point

» LEL = Lower Explosive Limits: is the lowest concentration of solvent vapor in air that can be ignited

» UEL = Upper Explosive Limits : is the highest concentration of solvent vapor in air that can be ignited

(The lower is the flash point of a solvent, the more highly flammable the solvent will be ! )

• Health hazards

» all solvents to be handled with care (ventilation, breathing apparatus, protective clothing, etc.)

Protective CoatingProtective CoatingBasic Knowledge



Additives which confer special properties to the paint:

• Rheological agent

• Anti-foaming agent

• Anti-settling agent

• Anti-skinning agent

• UV absorber

• Platicizer

Rheological agent

Protective CoatingProtective Coating3 Basic Knowledge


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Paint production Raw materials

Premix (millbase)

dispersion (grinding)

Final mix

packaging

storehouse

Site application

Part of vehicle and pigment, extender mixed

Agglomerates be divided into primary particles and wetting

the rest of the binders and additives are added, adjust viscosity and color

Protective CoatingProtective CoatingBasic Knowledge


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3-2 Coatings families: a brief overview

Others systems ( Polyurethane, Polyester etc.)

Coatings Families

Shop Primer

(Ethyl Zinc Sillicate, Zinc reach epoxy)

Soft Coatings Physical drying

(Chlorinated rubber, Vinyl Paint )

Hard Coatings

Chemical drying

Dry by oxidation (Oil, Alkyd Paints)

Epoxy base Coating

PSPC

Protective CoatingProtective CoatingBasic knowledge


3


Paint which dry by chemical reaction: Curing is obtained by mixing the base and the hardener in clearly defined proportions. A chemical reaction then occurs, causing crosslinking of the molecular chains. After curing, these paints provide a very hard film.

Base + Hardener Crosslink reaction

Crosslink Network



Basic knowledge3


Paint which dry by chemical reaction: Curing is obtained by mixing the base and the hardener in clearly defined proportions. A chemical reaction then occurs, causing crosslinking of the molecular chains. After curing, these paints provide a very hard film.

• The ratio Epoxy/Hardener is crucial for the final properties of the coating

• Temperature and Dry time have to comply with Manufacturer instruction to guarantee optimal conversion (To avoid solvent entrapment, crosslink default, vitrification etc.)

To ensure optimum coating properties

Protective Coating Protective Coating


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3-3 Notion of Coating System

• In addition to protect the substrate against corrosion, coating have to ensure others functionality such as adhesion, UV resistance, anti-fouling action etc. So we talk about Coating System.

Steel

Primer: (Adhesion and/or active corrosion protection)

Undercoats: barrier effect, ajusting thickness, compatibility with upper and below layers

Finish layer: Surface aspect, gloss, color, UV resistance

• Each coat layer is applied at a specified film thickness.


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Coating Process

•Environmental factors

•Surface preparation

•Coating application

•Coating inspections

4


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4-1 Environmental factors: Definitions and Influences

In order to obtain the optimum properties of a Coating System the applicator need to control the Coating Process

Drying timeDrying time

Surface PreparationSurface Preparation

Surface Preparation(eventually)

Surface Preparation(eventually)

Coating PreparationCoating Preparation

Overlap time delayOverlap time delay

1st CoatingApplication1st Coating

Application

x CoatingApplication

x CoatingApplication

Repairs(eventually)

Repairs(eventually)

Process applicated x times until to obtain the required thickness

Measurement and control of environnemental

parameters (T, NaCl, HR%)

Coating ProcessCoating ProcessBasic knowledge


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4-1 Environmental factors: Definitions and Influences Environmental conditions affecting the coating job are mainly:

• Surface temperature of the substrate (Condensation, Drying and Curing times)

• Ambient conditions, including:

» Temperature (Drying and Overlap times),

» Relative humidity (RH) (Drying and Overlap times, Conversion rate),

» Wind velocity (Drying and Overlap times, Health and Safety)

» Airborne contaminants (dust, chemical fumes, salt spray, oil,…)

(Adhesion loose, initiation of corrosion, failures)

Dew point is the temperature at which air is saturated with moisture. Below it condensation occurred and forbidden coating application.

Rust Scale if it is not remove prior to coating application will cause early failure. The loose top-scale is easy to remove, however the inner (black) hard scale is much more adherent.



4

4-2 Surface preparation

Surface preparation is the essential first stage treatment of a substrate before the application of any coating.

Correct paint application, ballast tank condition after 13 years (bulk carrier double bottom tank)

Poor paint application, ballast condition after 13 years (bulk carrier top side tank)

About 75% of coating failures would be caused by bad surface preparation



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The objective of surface preparation is:

• To ensure good adhesion properties between coating and substrate

• Surface cleanliness: to remove any contaminants which may be harmful to the performance of coating.

• Surface profile: create an “anchor pattern” and control it.



4


Sequence of cleaning and usual applicable methods

• Oil, grease – emulsifying solution or solvent.

• Soluble salts – water hosing, water jetting

• Mill scale, rust – abrasive blasting, water jetting, grinding, etc.

• Dust – blowing, vacuum cleaning

• Moisture – heating, ventilation



4

4-2 Surface preparation Cleaning method:

• Chemical: emulsifying solutions, solvents, pickling, etc. – oil/grease, or Mill scale & rust (pickling) .

• Thermal: flame cleaning – Mill scale & rust.

• Mechanical: by far the most widely used

» Manual and power tool - rust & old coating– Wire brushes, scrapers, etc.

– Disc sanding

– Grinding tools

– Chipping and needle gunning.

» Abrasive blasting – Mill scale, rust & old coating

The degree of surface cleanliness required, is determined by the generic type of paint, the aggressiveness of the environment and the projected service life/maintenance cycle of the structure

Manual and power tool cleaning:

• Low work efficiency , tiresome and maybe used in maintenance work or for preparation of substrate in non-aggressive environment.

Coating Process Coating ProcessBasic knowledge


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4-2 Surface preparation Surface cleanliness is to be checked:

• Before any surface preparation activities

• After surface preparation, before coating begins

remove sharp edges

remove weld spatter

suitable anchor profile

anchor profile(Base Metal Reading)

Hammer scale, Contaminants

cleaninganchor profile

(Base Metal Reading)

Hammer scale, Contaminants

cleaning

• ISO 8501-2,3:1998: preparation grades of previously coated steel/ welds, and other areas with surface imperfections.

• Correspond to the surface preparation standard, other exists, like the US Steel Structure Painting Council SP Standard



4

4-2 Surface preparationINTERNATIONAL STANDARD ISO 8501-1 : 1988 (E)

RUST GRADES

AB

C D



4• The text of the individual Standards are quoted literally



4

• Joint Surface Preparation Standard NACE No. 5/SSPC-SP 12 - surface preparation method using high pressure water for cleaning.



4

4-2 Surface preparation Suitable Anchor Profile:

Commercial Blast Cleanning

NACE 3

SSPC-SP 6

Sa 2

Brush off Blast Cleanning

NACE 4

SSPC-SP 7

Sa 1*

Near White Metal Blast Cleaning

NACE 2

SSPC-SP 10

Sa 2.5

White Metal Blast Cleaning

NACE 1

SSPC-SP 5

Sa 3

*ISO -8501-1:1988/suppl 1994

ISO -8503-1/3



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*ISO -8504-1:2001

Blasting is a collective name to describe methods using projection of abrasive particles at high velocity against the surface of a work piece. It is widely used and efficient.

Employed method :

• Dry blasting:

» Automatic mechanical methods: where the centrifugal force will actuate the abrasive directly when it is fed from the center and out to the wheel.

» Open nozzle blasting methods: the dry abrasive is mixed with compressed air in a mixing valve .

» Vacuum blasting: is a method by which the abrasive and dust are immediately removed by suction.

• Wet blasting

» Water blasting: use water, at pressures ranging from 200-700 bar, as the propellant for the abrasive.

» Hydro blasting (high pressure water jetting): at pressure more than 700 bar.

» Wet abrasive blasting and slurry blasting.



4

4-2 Surface preparation Different types of abrasives:

• The type and size of the abrasive used in blast cleaning have a significant effect on the profile or amplitude produced.

• Mineral Abrasives (ISO 11126/ 11127):

• Sand abrasives: which have the highest emission rate of particles

• Funace Slags (burning coal), Smelter Slags: The level of associate polluants vary depending upon the source of the coal.

• Mettalic Abrasives (ISO 11124 / 11125): They have the lowest particles emission rates.

• Iron and steel shot, Iron and steel grit.

• Organic plastic etc.

Open nozzle abrasive blasting:

• Compressor (capacity, pressure, separator etc); sand pot (abrasive size, salts, pressure gauge); nozzle and hose.

*ISO -8504-1:2001



3

4-3 Coating Application Mixing the different components (base, hardener, thinner )

Measure and control of Atmosphere and Substrate Temperature (/Dew point), HR%, Ventilation, Salt concentration*

1rst layer

2nd layer

3rd layer

O2 H2OO2 H2O Cleanness of coating surface before recoating

» To avoid discontinuities between layers and defaults

» To insure good adhesion between layers

Measure and control NDFT is the Nominal Dry Film Thickness*

Control Drying and Overlap time

» To be conform with TDS

» To avoid solvent entrapment

**ISO 19840:2004 *ISO 8502-9

SSPC-PA2



4

4-3 Coating Application Application workmanship:

• Preparation of paint

» Check the information of the can, such as type, colour, pot life, mixed ratio etc.

» Stirring, mixing and the volume of thinner mixed.

» Stripe coat (sometimes applied after paint application)

» Check spray preparation of equipment : power, hose, nozzle; flush out the old thinner, etc.

• Spraying technique:

» Spray pattern,

» spray distance to the substrate

» Crossing spraying,

» avoiding defect such as overspray and dry spray etc.

» Wet Film Thickness measured with regular.



4

4-3 Coating Application Application methods

Brush Application (for limited access zones, for small surfaces, welding, angles)

Advantage Disadvantage

• Use for limited access zones • Long time application and high costs



4


Roll Application (for plane and width surfaces)


• Four to Five times faster than brush application

• Not to be used for primer application

• Not adequate for aluminium filled paints, vinyl and rubber chlorinated paints



4


Pulverised Application

Airless Conventional Spraying

• The paint is provided by thrust, aspiration or gravitation until the fluid nozzle, then atomised by the air flux

• The paint is applied under pressure

•Its atomisation is due to the suction pressure.



4


Conventional spraying


• Faster than roll and brush applications

• Uniform and reproductible thickness

• Important looses

• Dry pulverisation (fog paint)

• Defaults applications in angles etc.



4

4-3 Coating Application Airless Pulverisation

Advantage Disavantage• Better efficiency (until 300 m2/h)

• High viscosity paint could be applied

• Lower paint losses

• Dry pulverisation (fog paint)

• Defaults applications in angles etc.



4

4-3 Coating Application Airless spray equipment :

• power source: air-driven, electrical-driven and other.

• Pump, check point: ratio, pressure of compressed air, oil separator, lubricating oil around piston rod, paint filter, paint filter, paint pressure .

• Nozzle: size of orifice and fan angle.Airless spray equipment



4

4-4 Coating Inspections Ensure that the work carried out is of a very high quality by

Inspection.

The tasks of coating inspection are:

• Prevent errors and mistakes to occur.

• Correct if do occur.

the inspection routines can be divided according to the progress of coating work:

• Before surface preparation

• surface preparation

• Before coating application

• Coating application

• Final control

• document



4

4-4 Coating Inspections Coating Process parameters have to be controlled

• Selection of the coating products: complete number and types of coats applied to a substrate in a predetermined order

• Primary and Secondary surface preparation (including cleanness before and after surface preparation)

• Mixing and thinning operations regarding each type of coat

• Checking of environmental conditions during all coating operations

• Coating application manner, wet film thickness (uniformity of film thickness), dry film thickness (per layer, and for the total multi-coat)

All these items are to make reference to specific standards to clearly define the Coating System

The Technical Data Sheet (TDS) is coating manufactures’ Product Data Sheet which contains detailed technical instruction and information relevant to the coating and its application. It is part of the Coating System definition.



4

4-4 Coating Inspections

Instruments used to measure environmental conditions are mainly:

• Surface-contact thermometer (magnetic surface-contact thermometer, direct-reading thermocouple / thermistors)

• Electronic Hygrometers are used to determine RH, Air temperature, and Dew Point temperature.



4



• Sling psychrometer (whirling hygrometer), used to measure the ambient air temperature (dry-bulb temperature) and wet-bulb temperature at the work site

• Psychrometric charts, are used to determine the RH and Dew Point temperature of the air, based upon dry-bulb and wet-bulb temperature readings. The wet bulb depression is the difference between the dry and wet bulb temperatures.

RH = 65 Dew T = 11 °C + 3°C

Dry = 18 °CWet = 14 °C

b_d = 4 °C

Dry = 18 °CWet = 14 °C

b_d = 4 °C



4


Dust Rating:

ISO 8502-3:1993

• provides pictorial ratings for the assessment of the average quantity of dust, rating:1,2,3,4,5;

• and also provides descriptive classed for the assessment of the average size of the dust particles. class 0 ~ class 5.



4

4-4 Coating Inspections Assessment of visual cleanliness:

Oil/grease determination:

• many methods are described for detection of oil and grease, unfortunately most of these are unsuitable for on-site use

• a simple method using a piece of chalk can often quickly decide if degreasing is necessary, as the figure.

Dust grades:

• Reference standard: ISO 8502-3:1993. Preparation of steel substrate before application of paints and related products – Test for the assessment of surface cleanliness.

• Evaluation of dust grades: generally according to the dust size and quantity to determine with the pressure-sensitive tape method. (not suitable to the plate of rust grade D)



4



• Solutions test and conductimeter (for Salts detection):

• To detect water-soluble salts, the most user-friendly method available today is to dissolve the salts that are present at the surface and to measure the conductivity of the water sample.

The sampling is given by ISO 8502-6, "Extraction soluble contaminants for analysis", the Bresle sampler.

The analysis is described by ISO 8502-9, "Field method for soluble salts by conductometric measurement".

Coating Process Coating ProcessBasic knowledgeC


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procedure to determine the soluble salts, as the figure.



4


The standard for assessment of visual cleanliness:

• The standard of ISO 8501-1: identifies three preparation grades, the various grades are defined by written together with pictures that are representative examples. (text see surface preparation)

» Blast cleaning: Sa1, Sa2 , Sa2.5, Sa3

» Hand and power tool cleaning, St2, St3

» Flame cleaning, FL

» Some pictures of the sample, as follows:

• Surface preparation standards for water jetting. See the previously mentioned : Joint Surface Preparation Standard NACE No. 5/SSPC-SP 12.



4

4-4 Coating Inspections Anchor profile Inspection:

• Rugotest No.3: has specimens for round and sharp profiles collected in one comparator. For greater roughness values there is even a division in fine and coarse grained finish.

Keane-Tator Surface Profile Comparator: has three different discs, designed by S (sand), G/S (steel or metallic grit), and SH (shot), respectively. As right figure



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• Anchor Profile Roughness :

In ISO 8503, two comparators are specified; one with profiles corresponding to blast cleaned surfaces using grit abrasive (reference comparator G) and one corresponding to blast cleaned surfaces using metallic shot abrasives (reference comparator S).

The nominal values for these profiles, identify the limits of the three grades fine, medium, and coarse.(Sa 3, Sa 2.5, Sa 2)



4


Instruments used to measure film thickness:

• Wet Thickness measurements :

The wet film gauge (ISO 2808) is a useful tool to measure wet film thickness on flat, even surfaces. When measuring the second coat, a soft first coat or, if the first coat is of a resoluble paint type, the results may be inaccurate.

• Dry Film Thickness measurements* :

The most used instrument in the field is the electromagnetic dry film thickness gauge. It is important to calibrate the instruments to zero and thickness similar to be measured.

*SSPC-PA2 : 2004



4


Instruments used to measure film thickness:

• Magnetic induction instrument, based on a principle of a low-frequency voltage in the probe create a magnetic field.

» The accuracy is within the range of + 3-5% of the reading.

» Keep the probe clean and free of paint and fillings

» Measurement should not be made too close to edges and corners.

» Adjustment:

– It is important to adjust the instrument according the manufacture’s

instructions using calibrated shims.

– Recommend to check adjustment of the instrument.

– Keep the steel plate clean and free of rust.



4


Instruments used to measure film thickness: Permanent magnet instruments (banana gauge)

• When measured: dial is turned forward to allow the magnet to contact with the film, then turn backward the dial slowly and evenly, until the sound of the magnet pull off, and the DFT can be read on the scale.

• The accuracy is within the range of + 5% of the reading.

• Measurement may be inaccurate when take on the underside of horizontal surface, or in area with vibration.



4


Instruments used to measure “adhesion”:

• Pull-off test* :

The pull-off test (ISO 4624:2002): Dollies are connected to the painted surface with glue. The force needed to loosen the dolly, is measured by the instrument. • Cross cut test, ISO2409.

Cohesive rupture

Mixed rupture

Adhesive rupture



4


After Coating application and drying Inspections are taken in order to note defects zones and undertaken Repairs.

The main paint defaults are:

• Delamination : Loss of paint adhesion

Causes : bad surface preparation, incompatibility between primer and paint layers, no adequate overlap time application

• Chalking : Separation between the pigments and the binder

Causes : UV ageing, Bad paint mixing, no adequate thinners

• Blistering :

Causes : Presence of contaminants (oil, rust, salts) on the metal surface, solvent entrapment.



4




• Cracking :

Causes : Application/drying temperature too important, too short overlaptime, formulation problems.• Checking :

Causes : Thickness of zinc rich primer too important

• Flaking :

Causes : Following to paint cracking



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• Cracking :

Causes : Application/drying temperature too important, too short overlaptime, formulation problems.• Checking :

Causes : Application/drying temperature too important, too short overlaptime, formulation problems.



4



The main paint defaults are:• Rusting :

Causes : Presence of holes, film porosity, substrate roughness too important.

• Orange peel :

Causes : Bad paint atomisation due to low pressure, nozzle near to the surface, fast solvent evaporation.

• Fish-eye :

Causes : Application onto oil, dust, water condensation, or incompatibility between paint layer.



Coating ProcessCoating Process4


Paint default:

ISO 4628 Paint and varnishes-Evaluation of degradation of paints coatings-Designation of intensity, quantity and size of common types of defect indicate the designation of degree of:

• blistering (Part 2),

• rusting (Part3),

• cracking (Part 4)

• flaking (Part 5).

Basic knowledge


ConclusionConclusion

The ability of the coating system to reach its target useful life depends on :

• The type coating system

• Steel preparation,

• Application and Coating inspection,

• Coating maintenance.

Basic knowledge4


ConclusionConclusionBasic knowledge on coatings

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Record and report

• Pre-job meeting (minutes):

» analyze, discuss the problem during the whole application process, and appropriate solutions adopted

• Daily log by inspector:

» Object ID: including site location, name etc.

» Work locations and date/time: details on area, etc.

» Ambient condition during blasting cleaning and painting.

» All data, reading, measurements etc. necessary to complete the required reporting of the project

• Non conformity reports

» Deviation description and reference document.

» Correct action

• Progress reports

» Work locations and date/time: details on area, etc.

» Initial condition/application details inspection result

» Remarks: deviation/ non-conformity.


ConclusionConclusion4 Basic knowledge on coatings

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Thank you for your attention

Documents

PSPC Training Material 3