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Removal of C5 insulation coating from electrical steel prior to copper plate

We are interested in copper plating a part made of electrical, non-oriented steel. The steel part has a C-5 coating (per ASTM A976 [affil link] ), which needs to be removed prior to copper plating. I don't know the details of this coating at this time, but have been told it is a phosphate coating incorporated with magnesium oxide. It is meant to increase the electrical insulation of the metal surface. I'm not a metal finisher, and would like to know what chemistry at what concentration and temperature would best remove this coating. I have read HCl and H2SO4 remove standard phosphate conversion coatings. Would the same apply to this "modified" coating?

Randy Lyle
Materials & Process Engineer - Tucson, Arizona, USA
August 30, 2010

A. My experience has shown extreme difficulty, if not a practical impossibility, to remove C5 from the surface of Electrical Steel. C5 is either 100% cover or striated, that is 50% cover; this is made so that motor stacks can be bonded. Part of the C5 is Ceramic Powder which once baked onto the material surface is the Devil to remove.
We have tried abrasive methods with almost no success.

Richard Miles
engineering - Baltimore, Maryland, US

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