EN 12944

ISO/EN 12944

nev(/T~ternatiOrjiks'tandard and, a European,/ positive vot~'s"byboth the International and Europe~~

This standard, which is both a Standard, has been given

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. , ~

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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

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. IS

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Deals with best practices in structural steel design from a corrosion prevention viewpoint.

ISO 1

L O ....... ­ ...

Covers surface preparation - reference to ISO 8501, ISO 8502, ISO 8503, ISO 8504.

ISO 1

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

ISO 12944-6

Laboratory testing of paint systems, particularly intended for those

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where sufficient practical experience is not yet available. Does not cover power tool cleaned steel specifically. ISO 12944-7

Covers application at works or on site, inspection and follow up. Also deals with reference areas.

ISO 12944-8

Describes how to and ancillary issues.

specifications for corrosion protection

ISO/EN 12944

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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.

ISO/EN 12944

TABLE 1 - CORROSIVITY OF ENVIRONMENTS

Exterior

Very low - low

15 years

16Ol-lm -

Low

2OOl-lm

Medium

200l-lm

C4

-

240l-lm

High (Zinc)

28 0 l-lm

High (Non Zinc)

C51

200l-lm

_

Low

C5M

280l-lm

_

Medium 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.

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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