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Corrosion of SS316 anodes in Silver Cyanide leaching solution

2001

Q. We are electrowinning silver from a cyanide leach solution using SS316 anodes. Pitting corrosion is occurring generally across the anode surface, and more so at weld areas. Can anyone advise the mechanism of the corrosion and any suggestions for different materials? Solution chemistry as follows.

NaCN 0.15-0.17%
pH 10.5-12
Ag 750 down to 220 ppm
Small amounts of Zn (100 ppm) and Cu (45 ppm) also present.
Operating volts 5.0-5.9

Stephen Lloyd
- Ashmore, QLD, Australia

A. In my experience low carbon steel works as well as stainless. One of the keys to keep the steel from dissolving is to maintain a pH of 12 or higher.

Pat Mentone
St Paul, Minnesota
2001

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