Metal finishing Q&As since 1989
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White burn, smoke on chrome plated parts?
Our company is experiencing a white smokey burn on parts coming out of the chrome every other rack. We have noticed a drop in the amps as carriers travel one foot station to station. We have checked the rectifier, cleaned and checked the buss for grounding. We are still experiencing the problem. My last conclusion is that we have gotten too much chrome behind and between the liner and tank. The tank was rubber lined new at one time, we had it patch several times but than went to a liner. The chrome solution has been tested ok. Any ideas that you can give us to help?
Steve Hathawaysupervisor - Barberton
December 21, 2010
Hi, Steve. I'd continue looking at the bussing. This sounds like a split-rail plating machine, where the last station must lift up, so its copper rail section is not part of the fixed copper rail.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 21, 2010
December 22, 2010
Steve,
A drop in amps when the carriers move from one station to another is normal for sliding contacts in conventional chromium plating.As long as it does not go to zero amps during the travel you'll be fine.
As your chrome solution has been tested OK, too high catalyst ( sulfuric acid )is not the cause of burnt in your case.
Also, watch out for the temperature of the chrome solution when plating. I prefer 40 to 45 deg.C . You should reduce amps with lower temperature.
- Penang, Malaysia
January 10, 2011
Hi, Steve,
Seems to me that you have electrical problem in your chrome tank.
Do you use life entry and life exit contact before entering and exit the chrome tank?
Normally if you have high current density whenever the part entering the chrome tank or exit the chrome tank you have big chance to get burning or smokey finish (short of whitewashing).
Or you have to check whether you have sparking during traveling in the chrome tank (between split copper busbar).
Or you have dirty chrome anode (passive,check the gas around the anode.
If less gas than normal or compare with other anode, take it out and clean it, and put it back with current or during production.
Best regards,
Tony
- Jakarta, Indonesia
Since the problem seems to be every other rack or sporadic, Maybe the racks are worn and have worn down or broken points or some other type of loose contacts under the plastisol. Maybe the hooks that contact the bar are corroded and dirty and failing to make good contact.
Frank DeGuire- St. Louis, Missouri, USA
February 16, 2011
February 18, 2011
Hi Steve, I had a problem like this myself one time. I consulted the bible (Canning hand book) and it suggests that the problem is either down to chemicals being out of spec in the plating solution, or too higher temperature for the currently density being used. We tackled it from the second option and increased the current density and
the problem cleared up.
Hope this helps
- Isle of Man Great Britain
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