Summary for alkaline copper plating Discussion
Alkaline copper plating and Rochelle salt issues are discussed in the context of a home-brew rochelle salt copper cyanide bath that was contaminated with phospho copper and was no longer plating properly. Raffy Eusebio asked how to treat the batch and how to deal with the phosphorus contamination. The reply notes that the question is hard to answer without more detail and cautions that the exact form of phosphorus matters. The answerer says they have no direct experience solving this specific problem, but suggests that activated carbon can remove phosphorus because of its large surface area. They also mention that aquariums use ferric oxide to remove trace phosphorus, and that ion exchange is probably not effective. The response emphasizes that the actual chemistry and contamination source are critical to choosing the right fix.
Q. How can I treat my alkaline copper batch which was contaminated with phospho copper?
RAFFY EUSEBIO
– CAVITE, Philippines
July 21, 2024
A. Hi Raffy,
As always, the fewer words in the question, the more abstract and difficult to answer.
I’m reading it that you are operating a rochelle salt copper cyanide plating bath, and it not plating properly in some respect, but someone accidentally added a small amount of pyrophosphate copper to it, so your assumption is that the phosphorous is the reason why … but it is a home-brew so no advice is available from a supplier?
I do not have any actual experience with resolving this problem, and hopefully a reader will come along who does :-)
Meanwhile, activated carbon does exhibit the ability to remove phosphorous, simply due to its huge surface area. Aquariums use ferric oxide to remove trace amounts of phosphorous. It is probably not removable via ion exchange. Again though, phosphorous comes in many forms and variations, so your actual situation may be critical towards receiving proper advice.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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Oscar Villalobos
plating shop employee – Guadalajara. jalisco, Mexico
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The following is a method from page 105 of
Analysis of Electroplating and Related Solutions
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a 5 ml sample into a 250 ml beaker [beakers on
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and allow to react for about 30 minutes stirring occasionally. Filter through a 41 or 31 paper and ash with water. To the filtrate in a 250 ml Phillips beader add 1 gram of manganese sulphate, 10 ml of 25% sulfuric acid and then exactly 50 ml of N/10 potassium permanganate
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to the normal starch end point. The ml potassium permanganate minus the mls sodium thiosulphate gives the permanganate used in the oxidation since the two solutions are equiv.
ml N/10 KMnO4 x .9375 = g/l COOK.CHOH.CHOH.COONa.4H20
I wish for you to note that the above procedure, in my opinion should be performed under an adequate exhaust hood and that all proper safety precautions should be observed.
Gene Packman
process supplier – Great Neck, New York
See page 456 of the 2007 Metal Finishing Guidebook. The last analysis is for Rochelle salt (potassium-sodium tartrate).
Kurt Sammons
– Inman, South Carolina