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Galvannealed vs. Zinc with Clear Chromate Conversion

We are a sheet metal fabricator for the electronics industry and we use a lot of galvannealed material (.036 to .060 Thk.) Our customers are always looking for documentation that compares the durability of galvannealed to post plated CRS with a Zinc, Clear Chromate finish.

We have also purchased a new deburring machine that uses a Scotch Brite belt and stainless steel wire brushes. It is reducing the zinc coating from about .0005 to .0003 or .0004. I need to get some proof that the finish will still be adequate when compared to a Zinc, Clear finish.

John Ridgway
- Franklin, Massachusetts

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Galvanneal or galvanizing will usually outperform zinc plating because it is thicker. While one should specify thicknesses rather than using loosely intepretable terms like "commercial zinc plating", zinc plating is usually about .0002" thick. But it's certainly possible to electroplate thicker than that.

I was under the impression that galvanneal is almost always painted, and your inquiry does not make that clear. If the material is painted, it's probably not going to make much difference whether it was galvannealed or plated and chromated since both will provide plenty of sacrificial protection against a scratch in the paint.

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

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WHAT YOU'RE LOOKING FOR IS ELECTRO GAL. THICKNESS IN COAT IS .0003-.0005" STEVE BATES
- PORTLAND, OR
 

With my past experience in sheet metal stampings I have found that once Galvanized or Galvannealed is stamped out or pierced you would lose that protection on the edges of both as the material is only coated. With Zinc plating spec to hold up to Salt Spray for 96 hour you gain the protection on the part completely. Correct me if I'm wrong.

Thad Gilman
- Minneapolis, Minnesota
January 18, 2012