Ask the Expert Question-and-Answer Archive

by Ron Joseph

December, 2003

CARC on Stainless Steel

Q. I'm coating stainless steel 304 with a MIL-P-53022 primer then with a CARC top coat. What type of pretreatment if any should be used on the stainless to insure good adhesion with the primer to the stainless steel?

A. You are getting yourself into difficult waters, because adhesion will be questionable at best. The only pretreatment that I know of is the use of a vinyl-butyral wash primer. You paint vendor can sell you a suitable product, but if I were you I would first experiment with the dilution ratio of phosphoric acid. If you have too much excess acid on the stainless steel after the wash primer has dried and cured, you will affect the epoxy primer MIL-P-53022. If this were my application I would try different acid ratios and then, after applying the entire coating system, I would perform both wet and dry adhesion tests. If you need help in this, please let me know.