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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Chrome contamination of nickel bath
Q. Would chrome contamination in the nickel bath interfere with the ductility test or cause failure?
Frank Vila- Windsor, On, Canada
2002
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A. Hexavalent chromium reduces the cathode efficiency and if high enough can stop plating. The hexchrome can be reduced to the trivalent state by adding hydrosulfite and raising the pH above 4.5 to form chromium (III) hydroxide which will be removed by the filter.  George Shahin Atotech - Rock Hill, South Carolina 2002 A. Hello Mr. Frank Vila, Yes you are correct the chrome contamination in the bath nickel cause problems with the ductility. José Francisco Costa- Aveiro, Portugal 2002 A. Hexavalent chromium causes poor adhesion, blisters, and lower cathode efficiencies. 0.01 g/l hexavalent chromium will reduce the efficiency by ~5-10%. About 0.1 g/l will stop the deposition of nickel. Sodium bisulfite will reduce the hexavalent chromium to trivalent chromium, which is not as serious a contaminant. There will be some reoxidation to hexavalent chromium at the anode, so the addition must be repeated periodically. The trivalent chromium can be partially filtered out above pH 4.2,and can be partially removed by dummying.  Sjamp van Esch - Eindhoven, The Netherlands 2002 |
I would like to say thanks to all the responses that I got. Is there a practical way of knowing how much the contamination is?
- Windsor, On, Canada
Q. Sir,
What are the in-house laboratory tests & equipment for finding out the presence and qty of iron, chrome and nitrate in nickel sulphamate bath, and removal of the same?
plating shop employee - Mysore, Karnataka, India
September 25, 2011
A. Hi Gaddam. Sorry, I am not familiar with nitrate contamination of a nickel tank; can you tell us how you suspect nitrate got into the nickel bath? Thread 46020, "Need a nickel nitrate solution analysis faster than EDTA titration" and thread 9065, "Impurities In Nickel Plating Bath" both address that topic however, and The Canning Handbook [on eBay, Amazon, AbeBooks affil links] warns to take care against nitric acid because serious contamination is not easily rectified.
Iron contamination can be addressed by raising the pH to 5.8 to 6.0 and filtering (per the same handbook). But perhaps more important than removing it is preventing it through pure chemicals, pure anodes, pure hooks, and immediately removing any articles that fall to the bottom of the tank.
Chromium contamination is removed by treatment with ferrous sulfate ⇦this on eBay or Amazon [affil links] , but the procedure in the Canning Handbook includes 7 paragraphs of details. If you search this site with the search term "chrome contamination of nickel" you'll quickly find at least 4 good threads focusing on that and other methods. Good luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2018
Q. I was wondering if an all chloride nickel bath is contaminated with chrome then the only way to reuse the nickel contaminated bath is to reuse it in a mixed nickel bath after the chrome is dummied out?
Is there an easier way to remove chromium from nickel chloride bath before it becomes unusable?
Johnny lai- Bellingham, Washington usa
September 21, 2018
A. Hi Johnny. I just added a very late response to Gaddam's inquiry which should be applicable for you; I don't think dummying is the way to remove chromium from a nickel bath.
Most people who use nickel chloride baths are using the highly acidic "Wood's Nickel" or similar formulations for striking, not for plating. If you are not trying to activate stainless steel or old nickel plating, an all-chloride bath is usually not the most appropriate. In your earlier letters you seem to indicate that you are a hobbyist or an amateur. If so, then I think you should be using a Watts Nickel bath, not all-chloride. So your question of whether the past presence of chrome means an all-chloride bath must be converted to "mixed nickel" doesn't really seem applicable: you should be converting it to a "mixed nickel bath" anyway :-)
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2018
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