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"Burning" defect in Chrome Plating

I have a customer with a bright chrome issue. We are not able to plate above 55 asf without burning. There is 32 oz. chrome with .12 sulphate and plenty of catalyst. The burning moves around and is in a different place on each bar. We just added more anodes and that did not help. We have had the rectifier checked and there is no ripple. We have tried fast ramping, slow ramping, high chrome, low chrome, high sulphate, low sulphate, temp. from 100 deg to 110 deg. We can not get over 5.5 volts. We did not find any stray currents and the tank is not grounded. We seem to have run out of things to look at. The Hull cell shows around 70mm coverage (5amp/3 min.)

Any suggestions?

Ken Kohlmann
Tech Sales - Manitowoc, Wisconsin
2004

sulphate is the primary catalyst, so what do you mean by "plenty of catalyst". Too much special additive can cause more problem than not enough. You can use a higher ASF if you take the temp to 120F. This also gives a much wider brite range of current density. Not that the plate rate will go down slightly, but the amperage can be turned up to more than compensate. Finally, what do you mean by "burned" and where is it on what kind of part? Take a look at your anode to cathode distance also.

James Watts
- Navarre, Florida
2004

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You mentioned that the burning moves around to different places on the rack, well it sounds to me that it is not a true burning but a so called "false burning" that is also called "white wash". If the burning is not at the high current density end of the parts, it is not a true burning. If this is the case, look for previous letters on this subject in this site.

Sara Michaeli
Tel-Aviv-Yafo, Israel
2004

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KEN,

CHROME BURNING PROBLEM,TRY TO 6 SECONDS RAM. MAKE SURE IS NOT A WHITE WASH PROBLEM. I DO NOT KNOW ,YOU HAVE CHROME PREDIP & NICKEL ACTIVATOR PRIOR TO THE CHROME. IF YOU DESCRIBE MORE INFORMATION TO EASY TO SOLVE THE CHROME BURNING PROBLEM.

Popatbhai B. Patel
electroplating consultant - Roseville, Michigan
2004