Metal finishing Q&As since 1989

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Masking powder coating / painting on mild steel

In our company, some of our electromechanical constructions are being made from mild steel sheets. Sometimes we use pregalvanized sheets but in some cases (welding...) we can't. As standard finish for protection we use powder coat painting with zinc phosphate as pretreatment. In some areas we want the surface free of paint (masked) for electrical conductivity. These areas are very sensitive to corrosion because zinc phosphate is not enough. If we provide electroplated zinc coating as a substrate under powder paint, the polymerization oven (powder paint polymerizes in 190 C) damages zinc's film and topcoat has no adhesion on the material

George Kontsas
plating shop - Larissa, Greece
2004

Please try it in the opposite order, George. Powder coat the parts and then, using the powder coating as a maskant, electroplate the zinc onto them. The selective powder coating can be done either with silkscreen patterns, or my masking the bare area of the steel which you will later want to electroplate.

I have seen this sequence used on decorative emblems, but with nickel-chrome or nickel-gold paint, so I see no reason why the powder coating shouldn't work just fine as a maskant for zinc plating.

Good luck!

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004