Dear Brimmer,

There is no such guidelines for coating selection followed in the industry. I have worked with Clients who requires coating to meet the design temperature. In my personal opinion, 10% than the max OT is quite sufficient and decent selection.

Coco- NACE PCS

Assuming the coating will be applied at ambient temperature / room temperature, I don't think it is expecting too much to require the Contractor or Supplier to provide a letter from the Manufacturer that the proposed coating is suitable for the intended application at continuous service temperatures between 23 degrees C & Max (???) plus 10 degrees C.

Contractors & Suppliers may find a temperature ratings on a data sheet and not really understand what the result implies. Likewise, the dilatants & plasticizers in a coating may not be stable at "continuous" elevated temperature and migrate out of the coating causing embrittlement, crazing or crack/shrink. Some coatings, (epoxies) might undergo a post cure phase that is beneficial. Some coatings will soften to a state of toughness, while others might easily be damaged by otherwise mild (typical) physical abuse. An elevated temperature could change the water absorption rate.

There are manufactures with R&D who confidently write such letters, companies that are too buried in bureaucracy to write these letters and companies that won't because they don't know (Compounders w/o R&D). There may be some exceptional companies to too buried in bureaucracy to write these letters but if they are, then if later a claim is generated, they will also handle it a a glacial pace.

It depends upon how much you trust what the process engineers and the control and automation engineers define for the system. It also depends on how you are setting the maximum long term temperature performance limit of the coating system (hint: letters aren't much use, detailed qualification test reports are). The engineers should give you the tolerance in the system and the likelihood of actually running the system for 'prolonged periods' at or near the tolerance limit. That should give you an indication of how much leeway you might need on the qualification test temperature from the paint manufacturer. A further consideration would be the actual criticality of the coating system in the corrosion control programme, e.g., an external coating system for atmospheric corrosion of a utility piping arrangement in a desert environment versus an internal pipeline coating for corrosive hydrocarbon transport.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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