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Remove Chromate Stain From Galvanized Steel

July 1, 2008

This a million dollar problem in the Galvanized Steel Industry.
Galvanized (Zinc Coated) Steel is either lightly oiled or chromate treated
to prevent "storage stain". Too much Chromate results in Chromate Stain.
Most material that has Chromate Stain (although only a cosmetic defect)
is immediately downgraded and sold at a loss.
There is has to be a way to clean the chromate stain off of the Galvanized
(Zinc Coated) metal without hurting the zinc coating. What type of cleaner will do this?

David Szydlik
Purchasing - Hustonville, Kentucky, USA

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July 15, 2008

Sir:
About 1985 I went to Quebec City because the galvanizer was producing a VERY UGLY chromate coating with various shades of green, olive drab, red, yellow and mixtures thereof. After two weeks of intensive laboratory work we reformulated a chromate quench that is virtually invisible. Areas where a drip remained dried to a very light sky blue drop. The company that I worked for is still using this formulation and maintaining it as required. This chromate quench requires the proper chemicals, the proper concentrations, and the proper pH. Normally the lifetime of the tank is several years. Thus the solution to your problem is education for the galvanizers from which you purchase your galvanized steel.
Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA