Q: We plate elongated parts that have approximately two sq ft of surface area. The process consists of a bright nickel followed by decorative chrome plating step. Rinsing is performed between the various process steps. We normally apply a thickness of 0.0003 to 0.0005 inches of bright nickel. Nine parts are plated on a rack. Each part has one electrical contact. The problem that we observed is poor leveling and the inability to cover minor defects on the surface. P. C.
A: Your e-mail did not give much information about the nickel plating bath you are using. I assume you are using the classic Watts bath. The most obvious cause of your problem may be that you do not have the proper concentration of brighteners in your plating bath. You might want to talk to your chemical vendor about getting a brightener system that has better leveling characteristics.
Assuming the chemistry of the bath is within specifications, you should determine if you are using the correct current density. A current density of 30–60 ASF is usually recommended. Based on the fact that you have nine parts on each rack and each part has a surface area of approximately two sq ft, the parts will have a total surface area of 18 sq ft and a current of 540–1,080 amperes is required. There are a couple of possible problems that you should investigate. Can the rack that you are using carry the number of amperes required? It also might be good to add a second contact point for each of the parts on the rack since the parts are elongated.