Q. I would like to know more about the black chromium plating process. Can you give me a procedure for the process? T.B.
A. Black chrome has been used for many years, primarily as a decorative finish. Most of the black chromium plating processes are proprietary in nature. The major problem with the process is getting consistent color and deposit characteristics. Sometimes a black chromium deposit is plated over a regular chromium deposit. There are proprietary processes based on both hexavalent and trivalent chromium.
A typical bath formulation is given in the table below:
| Component | Concentration |
|---|---|
| Chromic acid | 250g/L |
| Acetic acid | 260 g/L |
| Barium acetate | 7.6 g/L |
| Operating Conditions | Range |
| Temperature | 100°F |
| Current density | 40-90 ASF |
While the above formulation will give you a decent finish, you will be much better off if you use a proprietary formulation.
