plating, anodizing, & finishing Q&As since 1989
Adhesion problems with copper on old zinc parts
Adhesive problems with copper on zinc parts.
We do renovation of old car parts. Some of them are made of zinc. First we strip old layer, next we prepare (polish) this parts to finishing. First new layer is copper. We have adhesive problem with this first copper layer on zinc.
When we do new zinc elements (which don't have any layer) , we don't have adhesive problem. We do old and new parts in this same way. What is cause of this problem ?
Thank you for your advise.
I presume that the parts you are referring to as zinc are die cast from what we would call "pot metal". Typically zinc die castings may contain aluminum and lead. I would guess that it is lead on the surface, smeared by the polishing which is causing the adhesion process. It is relatively simple to overcome. After cleaning and activating the part, dip in 10% by volume hydrofluoric acid, rinse then copper plate.Gene Packman
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