A Case History

The following is a case history that I recently tried to solve. It is not in the usual format of question and answer, but I think it can be instructive to anybody involved in plating.


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The company in this case history manufactures parts made from cold-drawn wire that are zinc-plated. The parts were turning out very rough in many cases. The company discussed the problem with the steel supplier and the plating shop. As is often the case, the supplier of the cold-drawn wire blamed the plater, and the plater, of course, blamed the steel. A classic scenario that often occurs in our industry!

The plating company did up the ante and improved its cleaning process. This helped with getting a better finish, but not on a consistent basis. It was also determined that if the rough parts were stripped and replated, a good quality plate was obtained. After looking at all the obvious parameters with the cleaning and plating process, it was suggested that a sample of the plated parts be sent to a laboratory for analysis. The laboratory performed a rather time-consuming analysis and ultimately determined that there were very tiny metal particles adhering to the surface of the wire. What was the culprit? The wire was slightly magnetic, and even with a thorough cleaning process all of the particles were not removed. When the parts were stripped and replated, the particles were removed from the surface and the plate was roughness-free.

The question of course is why would the wire have a slight magnetic charge? The process of drawing steel through a die can cause a very slight magnetic charge on the material. Magnetic parts have always been an issue in the world of plating. In many cases, when this issue arises the parts have to be demagnetized (degaussed) before plating.

Why do I briefly discuss this problem? Because sometimes the obvious is not so obvious! I, for one, did not pick up on this initially. Next time you have a problem that doesn't respond to the obvious, perhaps it is a good idea to look for non-obvious answers.

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