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  for Metal Finishing since 1989
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Galvaprep is turning chalky

1998

I have a question regarding a product called galvaprep by Amchem. After applying the product to galvanized metal the substrate turned a white chalky color. What causes this?

Assistance greatly appreciated.

Thank You,

Bryan Colyer
paint - Stockton, California

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The purpose of Galvaprep is to convert the zinc metal and oxide on the surface to zinc phosphate, which provides an excellent paint base. The zinc phosphate coating is white. If you mean the coating looks chalky, but it is tight, you have a good coating. If the coating is powdery or wipes off, you are probably leaving the Galvaprep on the surface too long. Follow the directions on the bottle and leave the Galvaprep on the surface for 2 to 5 minutes, then rinse off and dry. It is best to paint ASAP after treating to avoid any possible contamination from handling.

Phil Johnson
- Madison Heights, Michigan
1998