Painting 316L Marine-Grade Stainless Steel

Question:

I saw your article about painting stainless steel. It was extremely informative and useful. Thank you from all of us who have read your advice. I noted your insistence on abrading the surface of the stainless steel (either through etching or mechanical abrading).

We intend to paint 316L marine grade stainless. But we are hesitant to abrade the surface, because we are fearful the rough surface will corrode faster once the paint wears off (and yes, in this high heat and high salinity environment down here at the equator, even 316L rusts). Is there any kind of paint you would suggest where abrading or etching is not possible? S. R.

Answer:

S. R., who works in Singapore, is referring to a question from J. A. in the October 2002 Painting Clinic about the effect on corrosion resistance by painting stainless steel. In the case where etching and abrading is not possible, you must revert to the classic pretreatment involving use of a phosphoric acid activated vinyl wash primer. The recommended procedure would be to degrease the surface and then apply the wash primer according to the supplier’s instructions. Since it is a pretreatment, the wash primer must then be coated with an epoxy primer, preferably an epoxy-polyamide, and then topcoated.