We purchase zinc plated electronic enclosures from an offshore company. 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?
I normally do not write about recent papers in the technical literature. However, a paper that appeared in the October issue of Plating and Surface Finishing was of great interest and requires wider distribution. The paper, “Unexpected Results from Corrosion Testing of Trivalent Passivates,” by T. Rochester & Z. W. Kennedy, discusses results using one of the standard tests for the presence of hexavalent chromium.
After silver plating machined aluminum we test the parts by heating to 175oC for one hour. During the soldering step a good percentage of the parts blister. Do you have any suggestions for eliminating this problem?
We are currently cadmium-plating fasteners in a cyanide bath and are finding that the finish turns black after four to six days. Parts come out of the process more or less bright white. After the cadmium plate we rinse and apply a chromate, rinse and dry.
One fastener is a little yellowish after a couple of weeks, but the others that are black were plated only four days ago. Can you make any suggestions as to how to solve this problem?
One of the tried and true testing methods for hexavalent chromium is the use of 1,5-diphenylcarbazide to form a colored complex with hexavalent chromium. The intensity of the color is measured colorimetrically. The colored complex does not form with trivalent chromium. Why has the test taken on added significance?