Painting Type 304 Stainless Steel
Q. I would like to know if it is possible to paint Type 304 stainless steel with a high-solids epoxy-type paint (per MIL-C-22750). If not, can you recommend a paint system that would be more suitable for this alloy? What type of primer is recommended for this surface?
Also, is it possible to achieve good adhesion without mechanical abrasion of the surface? If not, would abrading the surface compromise the corrosion resistance of the stainless steel? We would prefer to prepare the surface for painting by cleaning with degreasing solvents, but will this ensure good primer adhesion? D. D.
A. Generally speaking, an epoxy paint would be an excellent choice for painting Type 304 stainless steel. This statement applies to 100% solids, high- solids, low-solids and powder coatings. An epoxy primer would certainly be suitable for this application.
It would be wise to abrade the surface using something that does not cause iron particles to become embedded in it. Blast cleaning is an excellent method. In any event, the surface abrasion should be light.
A potential alternative to surface abrasion is a phosphoric acid-activated vinyl wash primer applied to a degreased surface and then top-coated with a liquid epoxy. This would be an excellent finish system for Type 304 stainless.
Solvent cleaning, if properly done, can also be used. The problem with solvent cleaning is potentially leaving diluted oily residue on the part surface. For this reason, if you choose this method of surface preparation be sure to change solvents often and, if you are wiping, change wipers often. I still prefer surface abrading.
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