Q. I have to apply powder coating to type 316 stainless steel castings. Should the parts be sand blasted, or can they be chemically etched? For the powder coating process, should parts be pre-heated in an oven before coating?—G.P.
A. I always have to ask why a product would be made of stainless steel and then powder coated. I know color is a factor, but it is still surprising to invest in stainless steel and then cover it with an organic coating. Anyway, the answer to your question is yes, the parts should be blasted. An acid etch process may also be effective but possibly more challenging to own and control. You will need an acid tank and fairly strong solution for it to be effective. You may find it easier to own a blast operation or send parts out for blasting. Blasting with a sharp media like garnet or aluminum oxide is probably best. It will create the roughened surface needed to provide an anchor pattern for the coating. Be sure to do some testing and confirm good adhesion.