Blisters Everywhere

Q. We purchase zinc plated electronic enclosures from an offshore company. The steel enclosures are plated in an alkaline non-cyanide zinc solution. We periodically have problems with blistering when the parts are subjected to burn in. We did not seem to have this type of problem when the enclosures were plated domestically. Short of bringing production back to the U.S., what can we do to minimize or eliminate this problem? D.C.

 

A. Alkaline non-cyanide zinc plating solutions are not very tolerant of poorly prepared surfaces. The most likely cause of this blistering is oil, grease or other types of soil on the surface. The cleaning steps must be investigated in more detail. The steps may not be working properly because of variation of cleaner temperatures or changes in the concentration of the components of the cleaner. Another common cause of this problem is small amounts of oil on the surface of rinse tanks. This manifests itself as sheen on the surface. Keep in mind that if there is oil on the surface of a rinse tank, when the parts are placed in the tank they pass through this oil layer and the oil is picked up on the surface of the parts.

Solving this problem may be a little more difficult since you will have to deal with it with companies that are offshore. However, it can be done.