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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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Best Metal to be used as Anodes in Electrolytic Cells
Q. I am an electrowinning in-charge of a gold processing plant and want to know what is the best metal grade available in the market for fabrication of anodes in our electrowinning circuit. Presently, our company is using the 316 stainless steel grade and it easily corroded that the life is about 2-3 months only.
The solution feed to the electrowinning circuit is a hot (80-90 oC) caustic-cyanide solution (1 - 2% caustic soda ⇦liquid caustic soda in bulk on
Amazon [affil link]
, 0.5 - 1% cyanide)containing gold,silver,copper and other base metals. Also,probably the solution contained some chlorides as a result of reaction of caustic soda with residual hydrochloric acids that adhere to the carbon during the elution process. (For info, part of our process in metal recovery from carbon is acid washing prior to stripping).
Thanks and regards,
gold mining and processing - Davao City, Philippines
2007
A. Planitized Titanium anodes will last a lot longer but are very expensive.
James Watts- Navarre, Florida
2007
Monel or Alpaca (cupronickel) wire bolted to 304 stainless plate in sodium hydroxide
Q. I want low resistance wire to connect to a stainless steel plate in an electrolytic cell, filled with a sodium hydroxide solution at no more than 120 °F. I settled on monel or alpaca (cupronickel) wire, both nickel/copper alloys, that are resistant to sodium hydroxide. The wire will be bolted or riveted to the 304 or 316 stainless steel plate. Will galvanic corrosion occur? The research I did seems to say 'not much.'
Bill Buford- San Diego, California, USA
January 29, 2018
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A. The safe bet is to use a strip of matching stainless and make connection outside the cell.  Geoff Smith Hampshire, England January 30, 2018 January 31, 2018 I got a response in another forum. It seems as if a nickel silver alloy with zinc would not work:
Submitted by Geir Moe on Wed, 01/31/2018 - 16:53 Hi Bill There is very little corrosion data of copper alloys in caustic service because copper contamination is objectionable. Also, alloys of brass and bronze with high zinc contents can be susceptible to dezincification. https://www.nace.org/Corrosion-Central/Corrosion-101/Dezincification/ Though additions of nickel appear to be beneficial to corrosion resistance. I have attached everything I have regarding corrosion resistance of copper alloys in caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] (sodium hydroxide) The ASM Corrosion Data shows an acceptable performance for a 75-20-5 zinc alloy, but realize this alloy only contains 5% zinc. I hope this helps UPLOAD DOCUMENTATION: PDF icon ASM Handbook of Corrosion Data.pdf PDF icon Material Selection for the Chemical Process Industry.pdf PDF icon MTI Material Selector or Caustic Service.pdf Bill Buford [returning] Questor - San Diego, California USA |
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