Letter 40066

Double zinc coating before powder coating  

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I am currently reviewing a project where a mild steel substrate is plated in a zinc cyanide solution and following that zinc phosphate coating. I am just curious whether any zinc phosphate would actually be found on the plated substrate. Would this double zinc coating provide any significant improvement against corrosion?

The substrate is finally powder coated with PE for external use. If the zinc phosphate coating does not present, would powder coating work well with a plated surface?

Kenny Loh
Researcher - Selangor, Malaysia

This "double zinc process" is probably doable, Kenny, but the usual approach is to zinc plate and chromate conversion coat the article before powder coating. Good luck.

Ted Mooney, P.E.  finishing.com Brick, New Jersey