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Problems with Clear Chromate Coatings

I'm a mechanical engineer using the end product of "Clear Chromate" coatings on 6061-T6 Alum. I don't have very much experience dealing with the conversion coatings but, I think I understand the basic process.
I see product with large color variations.....satin to glossy. The coating looks very clean with no color variation within the part. If part starts to show spotting on the sub-straight - what can be the causes? Is it not cleaned or etched properly? How does this effect the coating quality or is this only cosmetic?

Lindsey Howe
product designer - Charlotte, North Carolina
January 8, 2008

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Satin to glossy is not a color variation it is a brightness variation. Generally, the degree of brightness or gloss on the unfinished part is what you get on the finished surface unless the pretreatment process included steps to brighten the surface.

You need to specify what you need.

Gene Packman
process supplier - Great Neck, New York
January 30, 2008