Metal finishing Q&As since 1989

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Problems with copper foil electroforming process

We are attempting to plate a precision stainless tube with copper to about .004" thickness then remove the copper from the stainless mandrel. On our first try with a local plater, the mandrel was passivated to clean it and the copper came out looking blistered [.04-.06" diameter blisters, about .01" tall on 1/8"-3/16" spacing all over the part] but released freely. The blistering was also evident on the ID of the copper which made sealing with an O-ring impractical. For our second try, the passivation was only done for a minute or so and the copper looked great. We exposed the part to 350F for 1 hour prior to attempting to remove the copper. It was integral to the mandrel and could not even be machined off. We need to solve this problem but the next step is unclear.
I am sure that platers who make thin foil have these problems resolved. Can you refer us to a solution?

Brian Lundy
Military component manufacturer - SLC, UTAH
September 30, 2009

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You do not say whether your first attempt was heat treated or not - I presume not. I suspect what has happened is that the heat treatment at 350F has allowed some of the copper to migrate into the stainless steel tube and form an intermetallic alloy or a solid solution. My metallugy of copper systems is not as good as it could be, but I suspect it could have formed these with the iron, nickel or chromium in the stainless steel.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
October 10, 2009