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Removing Conversion Coatings

I'm seeking advice on how to effectively remove chromate conversion coatings (Class 1A) from aluminum alloys (6061-T651) without harming the substrate. There are anodized areas adjacent to the conversion coating that must remain in place. One additional constraint is that I'm dealing with a large part and would prefer the removal process to be done by hand. Any suggestions?

Keith Beckman
- Houston, Texas
2000

Keith,

There are several ways to accomplish that task.. but it depends in what you mean by "harming" the substrate.

You could mask the anodized areas, and place the part in a caustic etch for a brief amount of time, which won't do much, if any damage to the substrate. You could manually sand, or scotch brite the chromate off. Or.. if you absolutely cannot alter the finish of the substrate at all..you can try CO2 cleaning, which is essentially dry ice blasted onto the surface, which will remove the chromate, without any harm to the substrate, or the anodizing.

Marc Green
anodizer - Boise, Idaho
2000

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