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Alternate for Dichromate Sealing

2003

Dear Sir,

We do anodizing of sulfuric type. After anodizing, we do hot potassium Dichromate sealing to get yellow in color. Since we propose to eliminate the use of hexavalent chromium in the process, we seek alternate chemicals / process to get yellow color after anodizing.

Please suggest me, if any.

D. DHANASEKAR
- HOSUR, Tamil Nadu, India

I don't see why you could not dye them yellowish-gold before hot water sealing if you wanted. There are, I believe, also two-step processes and oxalic acid processes that would give you a yellowish-gold color.

But this idea of everyone insisting that their chrome-free parts must look toxic and carcinogenic is starting to drive me loony :-)

If you are bearing extra costs, plus suffering diminished corrosion resistance and other problems to make your coatings eco-friendly, talk somebody into allowing them to be green instead of toxin-colored for goodness sake!

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

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