Electroformed copper turns black when dissolving aluminum mandrel
A discussion started in 2009 but continuing through 2018
July 15, 2009
I am producing very low quantity copper electroforms with high precision mandrels made with 6061 T6 aluminium and, although I am very happy with the growth I achieve, the problem is that when I erode the mandrel using a 40 grams/litre solution of caustic it turns the copper black. Is there a way of either cleaning the copper with zero etching of the copper or, better still, preventing the black layer being formed in the first place?
Shop manager - Cornwall, England
July 22, 2009
A. Try to dissolve the copper oxide in a diluted sulfuric acid. If if does not work good enough, add 1-2 ml/l hydrogen peroxide
In any case, a slight etching of the copper will occur
chemical process supplier
Aluminium from dissolving mandrel plates out on electroformJanuary 9, 2018
Q. I have been electroforming copper onto aluminium formers. In removing the aluminium afterwards I have tried using HCl + Water. I found this to be a little slow and in some, strange cases, it eats the copper that I want left intact.
So I changed this to using Sodium Hydroxide to be used to remove the Aluminium. While this works really fast, when the temperature is set at 70 °C, I found a really unexpected result, the Aluminium seems to plate onto the copper. While this is not pure Aluminium it probably is Al(OH)4 or something like this, according to the chemical reactions. How do I avoid this? Presumably this is not usual.
University of Strathclyde - Glasgow, Scotland
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