zincate question

[carts69]

Can anyone answer this question i have? I have recently zincated an ally piece followed by acid copper plating, came out fine but in a couple of tiny areas i can still see the zincated underlayer, around the edges where plating was no doubt thinner, the question is can i dip the piece back in the zincate or will it ruin the copper finish i have obtained,can these small areas be touched in somehow? Thanks in advance.

[woodjames]

I've never been able to successfully "re-zincate" anything. It always ends up with a line of blisters around the are that was patched. I think what happens is the caustic nature of the zincate dissolves a bit of aluminum under the edge of the top plate. I may be wrong here, but I didn't think you can go directly to acid copper with a zincated substrate. Perhaps someone else could chime in on this matter. I've always gone to either bright nickel or flash copper after zincating. You wouldn't be able to see the zincate after an acid bath anyways, it's instantly dissolved. Try cleaning better, you may not have had proper coverage of the zincate to begin with. When I have had problems with zincate, instead of thin/non-existent plating in an area, it immediately blisters off, though it does coat. This might also be showing you that your ph of the copper bath is off, if you aren't getting good throwing power. Also, you mentioned alloy, you may want to try the de-smut/de-oxidizer, depending on what is in the casting. Hope this helps.