1、ISO/EN 12944MJM/19/07/97/GD Page No. 17/31/98This standard, which is both a new International Standard and a EuropeanStandard, has been given positive votes by both the International and Europeancommittees and can now proceed to being a full published standard. It is unlikelythat this will be the ca
2、se for all parts until mid 1998 at the earliest.It should be noted, that because of the approval given by the European committee,this standard will replace existing national standards such as BS5493 and DIN55928.The main problem I see at the moment is that it appears unlikely that the US basedspecif
3、ying houses will use the specification, but will continue to use SSPC andNACE guidelines.ISO 12944 states that it is designed for use by engineers who have some technicalknowledge in the area of corrosion protection, as well as knowledge of otherrelevant specifications.Many will find the durability
4、ranges to be extremely useful - this is the estimated timeto first major maintenance. This needs to be agreed between the interested partieswith reference to ISO 4628/1 to ISO 4628/5. It should always be realised that muchless effort is required to maintain a coating which has broken down to Ri2 tha
5、n onewhich has broken down to Ri3, for example.The durability ranges considered are:-Low 2-5 YearsMedium 5-15 YearsHigh 15 Yearsand 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 purelypresent to help the owner
6、 of the structure estimate sensible maintenance times.The guarantee time is generally shorter than the durability range, and there is nosimple relationship between the two.)ISO/EN 12944MJM/19/07/97/GD Page No. 2SUMMARY SECTIONSISO 12944-2 Covers the corrosivity of various environments and how these
7、canbe measured. Various anti-corrosive systems can then bespecified for these environments.IS 19244-3 Deals with best practices in structural steel design from a corrosionprevention viewpoint.ISO 12944-4 Covers surface preparation - reference to ISO 8501, IS0 8502, IS08503, ISO 8504.ISO 12944-5 Typi
8、cal paint systems by generic type for a given durability in agiven environment.ISO 12944-6 Laboratory testing of paint systems, particularly intended for thosewhere sufficient practical experience is not yet available. Does notcover power tool cleaned steel specifically.ISO 12944-7 Covers applicatio
9、n at works or on site, inspection and follow up.Also deals with reference areas.ISO 12944-8 Describes how to prepare specifications for corrosion protectionand ancillary issues.ISO/EN 12944MJM/19/07/97/GD Page No. 3PART 2CLASSIFICATION OF ENVIRONMENTSDefined from weight loss of metallic (low carbon
10、steel and zinc) specimens over adefined period of 1 year (not more and not less).There are obvious differences in this approach because of change of climate on ayearly basis, but this certainly helps quantify the corrosivity of an environment.ISO/EN 12944MJM/19/07/97/GD Page No. 407 May 1997TABLE 1
11、- CORROSIVITY OF ENVIRONMENTSExterior Interior D.F.T*C1, C2 Very low - low 80% specified d.f.t. Recommended that maximum d.f.t. is not greater than 3x nominal d.f.t. (this ismuch greater than we would specify and would certainly potentially createproblems). Reference to paint manufacturers technical
12、 data sheet. Note, all references are to airless spray application.ISO/EN 12944MJM/19/07/97/GD Page No. 7THICKNESSES/LIFETIMES FOR VARIOUS ENVIRONMENTS(Refer to ISO 12944-5)C2 80m Low150m Medium200m HighC3 120m Low Low corresponds to 2-5 years160m Medium Medium corresponds to 5-15 years200m High Hig
13、h corresponds to 15 yearsC4 160m Low200m Medium240m High (Zinc)280m High (Non Zinc)C5I 200m LowC5M 280m Medium320 HighISO/EN 12944MJM/19/07/97/GD Page No. 8PAINT SYSTEMSThose shown are examples for several environments:- Other systems having the same performance are possible. All paints for all syst
14、ems shall be suitable for the highest corrosion stress of thegiven corrosivity or immersion category. Documentation or guarantee stating suitability or the durability of a paint systemin a given environment - experience or artificial ageing tests where necessary.Standard arranges systems as follows:
15、-A1 to A5 According to bi nder in the topcoatOthers According to binder in the primer coatA1 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
16、C4.Where a paint system cannot be allocated to one of the Tables A1 to A9, fullinformation regarding:-Surface preparationGeneric typeNumber of coatsNominal dry film thicknessshall be given in the same way as indicated in the tables.ISO/EN 12944MJM/19/07/97/GD Page No. 9There are an extremely wide ra
17、nge of generic coatings included in the specification,and really these can only be considered as examples. Basically, paint types usedby all participating members have been included. No reference or allowanceappears to have been made to recognise the effect of the introduction of legislationto reduc
18、e solvent emissions, and paint types whose use is being restricted for healthand safety reasons are also included.Also, as in almost all specifications, there is no allowance or mention of what areoften perceived as key issues regarding coating systems, i.e. Drying times - handling times, overcoatin
19、g times Maximum overcoating times Effect of application conditionsIn general, more problems are encountered due to poor interpretation, ignorance ofthe above, or by use of coatings which are not sufficiently tolerant over a wide rangeof conditions.It is likely that most interest will be with the “hi
20、gh” durability systems, i.e. those withan expected life to first major maintenance of 15 years plus. With these it is alsolikely that the following environments will be most important:-C4 High CorrosivityC5-I Very High IndustrialC5-M Very High MarineThe C3 area of medium corrosivity will meet the 15
21、 year requirements with mostreasonable 2 or more coat schemes, giving minimum d.f.ts of 150-200 microns.ISO/EN 12944MJM/19/07/97/GD Page No. 10When considering the actual schemes listed, the following points are worth noting:-1. All coating systems, with the exception of those designed for immersion
22、, arevery multi-coat in type. This would almost certainly lead to a request fromany contractor to reduce the number of coats and utilise higher solidscoatings with higher d.f.ts.2. Some of the mixtures of systems, for example, overcoating alkyds withchlorinated rubbers, are not normally utilised.3. All specifications tend to be based on multiples of 40 microns, whereas in UKand many countries the multiples are of 25 microns, probably due to theinfluence of the US and 1 mil = 25 microns.
