ISO/EN 12944

This standard, which is both a nev(/T~ternatiOrjiks'tandard and, a European,/

Standard, has been given positive vot~'s"byboth the International and Europe~~ committees and can now proceed to being ~!~,}b[ished standard. It is unlikely

that this will be the case for ru! parts until n;Jfd 1998~ the earliest. , ~

\~'hi'-£'#/~/

It should be noted, that because of the approval given by the European committee,

this standard will replace existing national standards such as 8S5493 and DIN

55928.

The main problem I see at the moment is that it appears unlikely that the US based

specifying houses will use the specification, but will continue to use SSPC and

NACE guidelines.

ISO 12944 states that it is designed for use by engineers who have some technical

knowledge in the area of corrosion protection. as well as knowledge of other

relevant specifications.

Many will find the durability ranges to be extremely useful - this is the estimated time

to first major maintenance. This needs to be agreed between the interested parties

with reference to ISO 4628/1 to ISO 4628/5. It should always be realised that much

less effort is required to maintain a coating which has broken down to Ri2 than one

which has broken down to Ri3, for example.

considered are:­

Low 2-5 Years

Medium 5-15 Years

High >15 Years

and are assuming the coating has reached a breakdown level of Ri3.

(It is emphasised that the durability range is not a guarantee time. It is purely

present to help the owner of the structure estimate sensible maintenance times.

The guarantee time is generally shorter than the durability range, and there is no

simple relationship between the two,)

MJM/19/07/97/GD Page No.1

ISO/EN 12944

IS 10":;;"1''''--'')

ISO 1LO....... ­ ...

ISO 1

ISO 12944-6

ISO 12944-7

ISO 12944-8

SUMMARY SECTIONS

Covers the corrosivity of various environments and how these can

be measured. Various anti-corrosive systems can then be

specified for these environments.

Deals with best practices in structural steel design from a corrosion

prevention viewpoint.

Covers surface preparation - reference to ISO 8501, ISO 8502, ISO

8503, ISO 8504.

Typical paint systems by generic type for a given durability in a

given environment.

Laboratory testing of paint systems, particularly intended for those ,,---~~~~-" - - ""

where sufficient practical experience is not yet available. Does not

cover power tool cleaned steel specifically.

Covers application at works or on site, inspection and follow up.

Also deals with reference areas.

specifications for corrosion protection

and ancillary issues.

Describes how to

ISO/EN 12944

~-~

PARt 2 )~4__-~/

CLASSIFICATION OF ENVIRONMENTS

Defined from weight loss of metallic (low carbon steel and zinc) specimens over a

defined period of 1 year (not more and not less).

There are obvious differences in this approach because of change of climate on a

yearly basis, but this certainly helps quantify the corrosivity of an environment.

Very low - low

Medium

High

Very high industrial

Very high marine

Structures immersed

Structures

* Above thicknesses

<10-200 g/m2

(1.3-25IJm)

200-400 g/m2 (25-50lJm)

40-650 g/m 2

(50-80lJ m)

650-1500 g/m2

Exterior

pollution, dry.

and industrial atmospheres Moderate S02 pollution Moderate coastal CI)

Industrial and coastal.

ndustry with high humidity atmosphere

Heated buildings/neutral 'atm~pl:!9fes:

Unheated buildings, possible condensation

Production rooms with high humidity and air pollution

Chemical processing plants

D.F.T*

75IJm

200IJm

200IJm

240IJm (Zinc) 280IJm (Non-zinc)

320IJm

650-1 320IJm

ISO/EN 12944

TABLE 1 - CORROSIVITY OF ENVIRONMENTS

(Refer to ISO 12944-2)

Where single coats are applied higher film thicknesses will be required (see recommendec

specifications) .

MJM/19/07/97/GO Page No.4 07 May 1997

ISOIEN 12944

PART 3

STRUCTURAL DESIGN

ISO 12944-3, which covers basic design criteria, is really outside the scope of

protective coatings manufacturers. This can only really be fully implemented at the

New Construction stage or by major modification at a later date. Coatings are often

expected to alleviate, or help alleviate, corrosion problems due to design errors. In

this instance, it could well be that different coating specifications would be required

for these areas which could be thicker/more corrosion resistant than those used

elsewhere. Typically, if a certain area was subjected to frequent ponding of rain

water because of design, then either modification would be required to prevent this

or a different coating system could be needed.

ISO/EN 12944

ISO 12944-5

PROTECTIVE PAINT SYSTEMS

This section, and that on testing, are those most likely to be argued over and to

provide the greatest areas of contention.

In the areas of generic paint systems, almost every type which can be imagined has

been covered, and what appears to me a series of quite complicated matrices have

been put together. This is possibly why this part of the specification is not due for

completion until 1998 and will be the last section finalised.

At this time there continues to be much discussion on this section. and modifications

will certainly be made.

Currently, for example, it is indicated that both solvent based alkyds and water

based acrylics will dry at DoC, certainly we would not recommend this type of

condition for water based, and on conventional alkyds I would expect an extremely

negative effect.

• Note, the proposed definition and rider regarding zinc rich coatings. This now

becomes much closer to the SSPC SP20 definition than. for example, current

British Standards.

• Minimum film thickness should be >80% specified d.f.t.

• Recommended that maximum d.f.t. is not greater than 3x nominal d.f.t. (this is

much greater than we would specify and would certainly potentially create

problems). Reference to paint manufacturer's technical data sheet.

• Note, all references are to airless spray application.

ISO/EN 12944

THICKNESSES/LIFETIMES FOR VARIOUS ENVIRONMENTS

(Refer to ISO 12944-5)

C2 8Ol-lm - Low

150l-lm - Medium

2OOl-lm - High

C3 120l-lm Low

160l-lm Medium Medium corresponds to 5-15 years

200l-lm - High High corresponds to >15 years

C4 16Ol-lm - Low

2OOl-lm - Medium

240l-lm High (Zinc)

280l-lm High (Non Zinc)

C51 200l-lm _ Low

C5M 280l-lm _ Medium

Low corresponds to 2-5 years

High

ISO/EN 12944

PAINT SYSTEMS

Those shown are examples for several environments:­

• Other systems having the same performance are possible.

• All paints for all systems shall be suitable for the highest corrosion stress of the

given corrosivity or immersion category.

• Documentation or guarantee stating suitability or the durability of a paint system

in a given environment - experience or artificial ageing tests where necessary.

Standard arranges systems as follows:­

A1 to AS According to binder in the topcoat

Others According to binder in the primer coat

A1 All examples of systems for C2, C3 and C4.

A2 Systems for C2 (system not shown if it has high classification in A3, A4).

A3 Systems for C3 (system not shown if it has high classification in A4).

A4 Systems for C4.

Where a paint system cannot be allocated to one of the Tables A1 to A9, full

information regarding:­

Surface preparation

Generic type

Number of coats

Nominal dry film thickness

shall be given in the same way as indicated in the tables.

ISO/EN 12944

There are an extremely wide range of generic coatings included in the specification,

and really these can only be considered as examples. Basically, paint types used

by all participating members have been included. No reference or allowance

appears to have been made to recognise the effect of the introduction of legislation

to reduce solvent emissions, and paint types whose use is being restricted for health

and safety reasons are also included.

Also, as in almost all specifications, there is no allowance or mention of what are

often perceived as key issues regarding coating systems, i.e.

• Drying times - handling times, overcoating times

• Maximum overcoating times

• Effect of application conditions

In general, more problems are encountered due to poor interpretation, ignorance of

the above, or by use of coatings which are not sufficiently tolerant over a wide range

of conditions.

It is likely that most interest will be with the "high" durability systems, i.e. those with

an expected life to first major maintenance of 15 years plus. With these it is also

likely that the following environments will be most important:­

C4 High Corrosivity

C5-1 Very High Industrial

C5-M Very High Marine

The C3 area of medium corrosivity will meet the 15 year requirements with most

reasonable 2 or more coat schemes, giving minimum d.f.t's of 150-200 microns.

.. r _ _,F; W' !

ISO/EN 12944

When considering the actual schemes listed, the following points are worth noting:­

1. All coating systems, with the exception of those designed for immersion, are

very multi-coat in type. This would almost certainly lead to a request from

any contractor to reduce the number of coats and utilise higher solids

coatings with higher d.tfs.

2. Some of the mixtures of systems, for example, overcoating alkyds with

chlorinated rubbers, are not normally utilised.

3. All specifications tend to be based on multiples of 40 microns, whereas in UK

and many countries the multiples are of 25 microns, probably due to the

influence of the US and 1 mil =25 microns.

Hot dip Galvanized or Hot dip galvanized areas BS EN ISO 1461: 1999 Hot Dip Galvanized coatings on fabricated iron & steel articles ­specifications & test methods! This standard specifies the thicknesses (minimum & average 80 Mic DFT zinc coat) that should be followed, sampling methods ,selection of reference areas for testing & renovation methods etc. Then use ISO 10747 to issue quality certificates when ever required by the customer.

Note The durability of the galvanized coating depends on the type of environment as classified under ISO 129441 ISO 9223 ,& according to that in a rural environment the corrosion rate of Zn is less than 1 micron. (suitable for environment category C 1, C2) After galvanizing the total coating would be a combination of alloy layers (Fe & Zn) which is the maj ority & pure Zn.

Surface Cleaning: Free of zinc salts, dirt, contaminations and fresh water wash down and by dry

When viewed without magnification, the mild steel surfaces shall be free from visible Oil grease and dirt and from poorly adhering mill scales, rust paint coatings and foreign matter, moreover the metallic substrate shall give rise to a metallic sheen. Dampness with salty finger prints not Acceptable