Summary for tin-zinc plating Discussion
Tin-zinc plating is the focus of this thread, where Chris Renis reports that parts specified as a cadmium replacement showed conflicting XRF and EDS results. After cross-sectioning, he believed he saw a nearly pure tin layer over a zinc base layer and asked whether that could really happen. The reply advises caution: the evidence is too flimsy to accuse anyone of fraud, but one plausible explanation is that the parts were actually plated in two separate steps — zinc in a zinc bath followed by tin in a tin bath — rather than being a true alloy deposit. The answer does not confirm the cause, but it emphasizes that the cross-section appearance could indicate layered plating and that the situation needs careful study.
April 1, 2013
Q. We are currently purchasing parts with a tin-zinc plating called out as a replacement for Cadmium. We were seeing issues with the plating and decided to do alloy analysis via XRF and EDS, which yielded very different results. Upon cross-sectioning a part, it was discovered that a nearly pure tin layer had plated over a zinc base layer. Our plater does not believe that this is possible, but the photo appears to show it to be the case. Any ideas on whether or not this is possible and what could cause this issue if it indeed is plating in layers?
Chris Renis
Engineer – Chicago, Illinois, USA
A. Hi. This seems to require really careful study. I would never accuse anyone of fraud based on such flimsy evidence, but it sounds like one possibility could be that it actually is a layer of zinc done in a zinc plating tank followed by a layer of tin done in a tin plating tank. Really interesting!
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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April 1, 2013