The effect of current efficiency on electroplating

During the electroplating process, it can be seen that bubbles sometimes precipitate on the plated parts. Tests have proved that these gases are hydrogen. This indicates that a part of the current in electroplating is consumed by the hydrogen evolution reaction. That is to say, the current is not 100% used for the precipitation of metals. We call the ratio of the current used to plate the metal to the total current through the plating tank as current efficiency.

The current efficiency of different plating types is different: some are very high, such as acid copper plating, silver plating, etc., up to 100%; some are lower, such as cyanide Electrochemical copper plating, alkaline zinc plating, etc., are only about 60%; some are very low, such as chrome plating, etc., less than 15%.

Plating species with too low current efficiency not only waste more electric energy, but also cause instability of the plating solution, and it is easy to produce gas traps. Therefore, when the process permits, a plating solution with higher current efficiency should be selected as far as possible.

In theory, the current efficiency is defined as the ratio of the mass of the substance actually deposited or dissolved on the electrode to the mass of the precipitated or dissolved calculated theoretically, usually represented by the symbol л.