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Thread coverage problem in Cadmium Plating

I am the QC Manager for a small nut manufacturer currently experiencing problems with thread coverage. Plater states that the parts look great when he is finished, but with in a few hours or weeks the threads get very dark and look as though there has never been any plate there. We are having enough rejections to cause me a great deal of irritation. This is a long time vendor and I really don't believe they are doing anything intentional.

Laura Frey
QC manager for a small locknut manufacturer - Canton, Texas USA
November 24, 2009

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First of two simultaneous responses --

Is his cleaning not getting the goo out of the threaded holes? Is his CN/Metal ratio too low? Is his carbonate too high?

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

November 25, 2009

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Second of two simultaneous responses --

Second guessing the plater so you can blame him or give him advise is not what I am trying to help you with. It does seem possible that the plater is having issues with throw, the amount of plating in low current areas. Without knowing more about the manner in which these are plated, the size of the part, etc. It is impossible to be more specific since there are other possible causes: i.e. type of material being plated, load size, etc.

Gene Packman
- Great Neck, New York
November 27, 2009

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We've encountered this with our internal threads on occasion, especially with Type I Class III requirements. If there is not sufficient plating in the threads, especially at the bottom of the thread pitch, it will discolor quickly. If tolerances allow, have the plater hold the thickness to the high side of the range. I'm assuming the plater has good process control and it's not a throwing power issue.

Jim Conner
Anoplex Software

Mabank, Texas USA

December 2, 2009