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topic 0250

Etching of cobalt-chrome alloys, electropolishing

A discussion started in 1996 and continuing through 2009.
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I am looking for any and all information on surface etching of cobalt chrome alloys using an ambient temperature bath.

David B [last name deleted for privacy by Editor]

January 3, 2009

Hi, David. We need more info please? :-)

Sorry but it's just not clear whether you wish to etch a cobalt-chrome alloy . . . or whether you are trying to electropolish it but it is getting etched instead of electropolished . . . or what the situation is. It's not clear if you require an ambient temperature bath, or you are telling us that the bath you are using which is causing the etching is ambient temperature.

It's not clear if you are successfully electropolishing a number of other stainless steels but the cobalt-bearing one is causing problems that the nickel-bearing steels are not.

The most common causes of etching are excess water (and at ambient temperature you have no evaporation to deal with the drag-in) and insufficient current density.

The Electroplating Engineering Handbook has a good chapter on electropolishing, and Metal Coating Process Corporation runs an electropolishing school. Good luck.


Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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