Rhodium Process Guide

Rhodium plating is one of the lesser known forms of electroplating. Many factors affect the properties of the deposit and a reliable process will ensure consistent thickness, reflectivity, and adhesion. The fishbone chart below can serve as a guide to eliminate common plating issues found with rhodium.

Gold copper intermetallic

Q: I gold plate copper alloys and over time my customers are returning parts because the gold is changing color. How can I fix this issue? 

A: Plating over these substrates presents an interesting problem. Copper has a tendency to migrate into gold and form an intermetallic (or alloy). This causes discoloration over time. To avoid this I recommend first plating 100 microinches of nickel over the substrate as a barrier layer. In addition, utilize sufficient agitation and gold content in the tank. I recommend 0.5 oz./gal to ensure a smooth and consistent deposit.

Zinc contamination in nickel tank

Q: How can I reduce nickel plating defects over zinc die-cast substrate? 

A: In the case of zinc die-cast the substrate is directly responsible for introducing zinc contamination to the nickel tank. Zinc is a toxin to nickel plating baths and will significantly reduce performance and bath life. It is important to address this issue early in the process which is typically:

- surface prep
- copper plate
- nickel plate
- post treatment

The best corrective action is