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Carbon smut problem before chrome plating

adv.    

May 15, 2008

We are having problems after reverse etching carbon steels of carbon smutting the surface to be plated. could you suggest a suitable solvent for its dissolution or a chemical which we may add to a hard chrome bath so that the carbon occurred on rev . etching forms a complex or a removable byproduct?

Application is for Hard Chrome plating a water cooled chill roll of 25 microns and having a hardness of 45 Hrc

Surojit Bhattacharjee
plating shop incharge - Calcutta,W.Bengal, INDIA

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My thought is that you are etching at too high a voltage and / or too long. If reducing the etch does not help, put in a chromic acid etch tank and you will not have the problem.
There is a high amperage anodic/cathodic process that is published, but I do not like it. I have used a sulfuric and hydrofluoric etch at low amperage that forms a very tight smut that can be plated over with good adhesion in SOME cases. It requires a lot of trial and error testing.

James Watts
- Navarre, Florida
May 16, 2008

adv.