Gas pits or hydrogen pits

It is not unusual for a portion of the applied electroplating current to split some of the water in the plating solution into hydrogen gas and oxygen gas instead of depositing metal . You can review our "Faradays Law" page to understand this situation better.

The hydrogen gas will be generated at the surface of the parts being plated and will form tiny bubbles which look similar to those in ginger ale.

These bubbles will tend to adhere to the surface and the plating will grow around them, causing small pits. If these are looked at with low power magnification, they will be revealed as hemispherical and shiny. Not all pits are gas pits, of course, but examining pits with a jeweler's loupe will tell you whether they are gas pits or not, which can be very helpful in troubleshooting plating problems.

Gas pits are a very common problem in nickel plating, and are counteracted by wetting agents in the plating solution to keep the surface tension low, and by vigorous air agitation ⇦ huh? to knock them loose.