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Chemical conversion coating on top of anodizing

(-----) September 1, 2021

Q. Is orange colour will fade in the anodized parts with the thickness of 5 to 6 microns when immerse the anodized parts in Bonderite M CR 600 chemical for chemical conversion process for 30 to 40 seconds.

Vasudevan Sivaraman
- Madippakkam, Chennai, Tamil Nadu, India

September 2021

A. Hi cousin Vasudevan. Yes it may fade.

Indian English is different than American English, so I'm not sure I'm understanding the question. Further, we beg people to introduce themselves and explain the details of their own actual situation, not post abstract questions :-)

But it sounds to me like you have anodized components which are dyed orange in color, and presumably properly sealed, and now you want to dip them into a chemical conversion coating tank for some unknown reason.

We could guess that maybe you have components that require anodizing in some areas and chromate in other areas -- in which case you are not doing things in the right order :-(

But that's only a wild guess, so before we go off on wild goose chases, please introduce yourself (are you from the anodizing shop, or are you the buyer?) and your actual situation please. Thanks!

Luck & Regards,

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

September 28, 2021

A. Hi Vasudevan,

The only application I am aware of for using a conversion coating product AFTER anodize is the extremely rare use of a trivalent (blue) chromium CC bath at high temp, used in lieu of nickel acetate seal (got this tidbit from my BASF guy, have never been asked to actually use my CC +3 bath as a seal!).

Hex (yellow) products are a much lower pH and would be detrimental to anodize. The surface would become powdery, like leaving them in a nitric dip too long.

Normal routine is conversion coat, mask, strip, anodize, seal, unmask. As Ted says, it seems you might be doing things a little out of sequence...

Rachel Mackintosh
Lab Rat and some other things - Greenfield, Vermont

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