Q. We are having problems with the formation of gas pockets in our cadmium plating bath. The pockets form inside some of the parts being plated. The plating bath used is cyanide based, and air agitation is not recommended for this bath. Mechanical agitation does not seem to solve the problem in all cases. Is there something else we might do to prevent the formation of air pockets in this plating bath? B.Z.
A. Cyanide cadmium plating is not 100% efficient. The end result is that some hydrogen is generated. This hydrogen is probably the source of the air pockets you describe. Mechanical agitation should work for you if it is designed to tilt the parts so that the gas is released. This is easier said than done.
The classic solution to this problem is to design racks in such a way that the gas can be freely released. In doing this, you may end up with parts that function as cups and will drag plating solution out of the tank. This means that special care will have to be taken when removing the parts from the plating bath and rinsing the parts.
Another alternative is to use manual agitation. This works in many situations but is dependent on the operators manually agitating on a regular and consistent basis.
The bottom line is that there is no silver bullet available to completely solve your problem.