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  for Metal Finishing since 1989
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Why is our chromium plating darker than usual?

I have a bath of hexavalent chromium, and now its darker blue than few moths ago, can be this due to a high trivalent Cr?

Daniel Hernandez
plating shop - Bucaramanga, Colombia
2007

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In my experience, hexavalent chromium baths are bright orange or red and trivalent baths are green or blue. I would suggest you have a very high level of trivalent chromium in your bath.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2007

A combination of copper, iron, nickel and trivalent will turn a hex Cr bath very nearly black. The analysis for trivalent is straight forward by oxidizing the tri to hex and analyzing the same way as normal. From this value, you subtract the normal Hex reading. The balance is tri. The oxidizer to use is one of several, depending on which book you use.

James Watts
- Navarre, Florida
2007

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2007

Dear Friend,

Yes if the chrome bath is blackish blue then your trivalent may be high.
For this use dummy treatment by reducing your cathodic area to 50% and use high current over night and check the tri velent again
Regards

S.V. Aurobind
plating process supplier - Bangalore, India