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"Hard chrome on copper blisters at 130C"
We have a 1" x 1" x 1" hard-chrome plated copper heater block that is developing blisters when the temperature is held at 130C. The plating ranges from 0.0002 to 0.001 inches thick. The blisters eventually fall off (they actually pop off at times), leaving 0.25 to
0.5 diameter unplated copper. The block is heated by a cartidge heater inserted into a hole in the block. Temperature is controlled with a PID controller and a thermocouple inserted into another hole in the block. We call our MIL spec hard chrome, but have a serious problem with the result. We'd greatly approciate any suggestions as to what is causing the problem so we can help our plater solve the problem.
manufacturing - Chicago, Illinois
It's admirable to want to help advise the plater how to fix it, but probably not realistic to expect that someone can give you a quick tip that will fix things. But, to give it a try, please remind your shop that copper must not be reverse etched because this causes copper to dissolve at just the wrong time, and makes the chrome non-adherent. Rather, after cleaning, which could be as simple as Pumice [affil. link to info/product on Amazon] scrubbing and rinsing, the copper must enter the chrome tank "live" (cathodic).
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Thanks Ted!John Bussan
manufacturer - Chicago, IL , USA