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Mysterious reduction in spring wire thickness during plating
August 22, 2013
Q. We manufacture a Compression spring out of 0.026" tolerance ±0.0003 wire diameter music wire per ASTM A228. We send the part out for a commercial .12 mil min. thickness tin plate. Weird thing occurred when we received the parts back and measured the wire diameter cross section: the wire diameter was measuring 0.0251" on average. Could the electroplating process have removed some of the base material? We measured the tin plating thickness at around .2 mil average. We are planning to send the spring out to a lab for evaluation. Just looking for any insight.
August 31, 2013
A. Hi Chris
Electroplating does not dissolve the base metal but the pre-treatment certainly can.
I would suspect that the wire was grossly over-pickled. Don't be surprised if the plater denies this!
You should also be aware that acid cleaning of piano wire can lead to serious hydrogen embrittlement. I have seen springs self destruct after a modest acid dip.