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Cyanide copper strike pH adjustment alternatives
Q. Hello all,
I'm experiencing a sharp pH increase in my cyanide copper strike tank. I've always used tap water for makeup. Our water must have some pretty good buffering capacity (it's not good for much else...very high TDS and pretty hard) because the pH remained fairly stable. Well we went and purchased a nice RO unit and most all my rinsing/water problems went away. Unfortunately so did my buffer. I'm running a lot of Zamak 4 zinc alloy through this tank and it doesn't tolerate a pH of 12.8 too well. I'd prefer not to go back to adding tap water. What is a good way to reduce the pH in this tank without decanting?
Jeff WebsterPlating shop - Peoria, Illinois, USA
2005
Sulfuric acid, little at a time.
Good luck
Jon Diamondsilver plater - Berkeley, California
2005
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Ed. note: For those who might not know, adding acid to cyanide releases poisonous hydrogen cyanide gas. In fact, that's exactly how California's gas chamber executions worked. Don't even think about adding acid to cyanide unless you are experienced plater, trained in this, and know exactly what you are doing! Even then I don't think I'd do it.
I think sulfuric acid is not a good way because the smell is bad, You can Use acetic acid [on eBay or Amazon].
Gabriel Ramirez N- Toluca, Mexico
2005
I don't think I've ever reduced the pH of my copper tank in 24 years of plating on all grades of Mazak. There's a step wrong somewhere before the copper plating, Jeff.
Khozem Vahaanwala
Saify Ind
Bengaluru, Karnataka, India
2005
Sodium bicarbonate will safely lower the pH of cyanide copper to ~10.0 (i've never tried to go lower than this but it may be possible), I make a slurry with water before adding it. I have to assume that it drops the pH due to the formation of carbonic acid when you add the bicarbonate to water.
James Jones- Minneapolis, Minnesota, USA
September 26, 2012
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