Peeling and Barrel Nickel Plating
Q. What causes peeling of nickel layers in barrel plating? We do not see this problem all the time but when it occurs the nickel layers peel from each other, very much like an onion.
Do you have any suggestions on how this can be prevented? H.K.
A. The symptoms you describe suggest that your nickel is becoming passive during the nickel plating step. As you know, nickel easily passivates. A fresh nickel deposit reacts very quickly with oxygen in the atmosphere to form an oxide on the surface. Once formed, the nickel deposited on top of this oxide will not adhere very well and will tend to peel.
Start your troubleshooting by determining if your parts are immersed in the plating solution during the entire plating step. If your barrels are overloaded, parts may not be completely immersed and can form oxide on the surface.
The next step is to look at your electrical connections. Current interruption can play a role in peeling. Are your barrels properly seated in the saddles? Is your bussing clean? Salts can build up in contact areas and cause partial loss of conductivity. This can cause bipolar effects in the barrel and passivation of surfaces.
Don’t forget to review the chemistry of your plating bath. An excess of organic material can increase the likelihood of forming nickel layers on your parts.