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Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)
by Randy Taylor, Advanced Tooling Corporation.
Copper Peeling Off Parts
Q. I am having problems with the copper peeling off my parts. Could you tell me what could be wrong?
A. You don’t mention the type of copper plating bath, but most of what I can tell you applies in either case. Here are some general things to consider...
Initially do a careful walk thru the plating line. Take your time and check for oil residue floating in tanks, maybe from an occasional drip from an overhead hoist or gear drive trolley system as an example. Peeling plating can be caused by a number of factors, oil or some other un-soluble residue are usually the first things to look for. Lead contamination is especially troublesome in a copper plating bath. Check part handling from unpacking to rack loading to see if an unsuspected contamination is occurring. If parts are grit blasted or blown off with compressed air, verify the air supply free of water or oil contamination. If parts are hand polished or electro-polished, check for rouge or polishing compound or other chemical residue on parts. If parts tend to lie around the shop for extended periods of time, even over night between process steps, they may be become contaminated by dust, humidity, foreign matter or rust.
If those things check out, dig a little deeper.
1.) verify the part base material is compatible with the preparation steps for that material. For instance if the material is stainless or hardened steel, it may require additional preparation like a nickel or copper strike. In fact, many copper plating processes start with a copper cyanide strike to prevent immersion copper during start up.
2.) check pre-treatment process tanks and solutions, i.e., degrease, soak cleaning, electro-cleaning, acid etch for condition, age and chemical content.
3.) check for copper plating bath for correct temperature, condition, agitation if any and chemical content.
4.) Check rectifier for DC output, verify amp & volt gages are accurate
5.) Check DC cables, tank bussing for correct polarity and continuity
6.) verify hanging hooks, racks, fixtures are in good condition and adequately sized to carry the correct amount of DC current, not just for plating but during electro-cleaning, nickel striking or any other electrolytic process.
7.) check anodes for purity, size and condition. Look for signs of oxides forming on anodes, or electrical inactivity. The general ratio of surface area or anodes to surface area of parts (cathodes) should be in the neighborhood of 1:1 to 2:1.