What ISO and NACE standards are you comparing, as, typically, C5M and CX systems go to a maximum of 120 deg C? If the plant is right on the coast, within a kilometre, or so, the client may want to consider a CX atmospheric classification with ISO 12944-9 testing. An alternative would be NORSOK M-501, System 1 - again to a maximum of 120 deg C. The main paint manufacturers will generally have a listing of their NORSOK qualified systems, but you should check their qualification test reports in detail.

If you want peace of mind, and ease of selection, thermal spray aluminium would be the way to go for the quoted conditions. Long life, low maintenance.

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

May seem a minor point but the current version ISO12944 (various dates depending on part) no longer splits the onshore C5 category into M and I sub categories, there is just C5. There is the additional category CX which covers Offshore areas, extreme pollution and humidity, or tropical atmospheres. ISO 12944-2 Annex A and Annex B 2.5 deal with temperature but that is more to do with time of wetness.

Is it reasonable to assume the elevated temperature in this case comes from the process rather than the atmosphere? If so, and the temperature is continual, the concern might be more on the impact on the resin base of the paint than corrosion risk?

Cheers

GG

Dr Jones, I should have been more specific, its NACE TM0404/TM0174. However, after a bit of digging, I doubt that the ISO12944 scope exceeds applications beyond 50^oC.

GGedge, I think the client provided old spec sheets, it is C5. Yes the elevated temperature is from the product which is at around 70^oC. The 130^oC is a buffer against an upset condition.

By the looks of it, the paint requirements are unrealistic, i.e. ISO12944 and 130^oC

Thank you.

@Dr Jones, when you say 'long life, low maintenance' for TSA coatings, how does it quantitatively match with the C-corrosion ratings of the ISO 12944 std?

I think you are outside the scope of the corrosivity categories as given in ISO 12944 because of the service temperature. The corrosivity categories given in that standard are the same as those in ISO 9223 which in turn use data from exposure samples up to 28.7 Celsius. I would be inclined to explain that to the client and suggest an alternative is appropriate for this application.

In relation to TSA, you might refer to ISO 12944 Part 9, Table 3 Note a), which is for a CX offshore service. There are also various references in that part of the standard to "high durability" which is ISO speak for a life to first maintenance of 15 to 25 years and it is supposed to cover coating up to 80 Celsius. Some might consider this a bit of a contrived argument but if you need to use the ISO then it is probably the best you can do.

NORSOK M501 System 2A is sealed thermally sprayed aluminium for use in offshore application at elevated temperature but unfortunately that standard doesn't include a durability rating. Given the scope of application it is reasonable to assume it is similar to ISO 12944-9. I think part of the intent of Part 9 was that it would replace or be accepted as an alternative to NORSOK M501.

Cheers

GG

Thank you GG. I found the paint and the client is in agreement with the suggestions on this thread.