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Stainless steel "dissolving" in electrocoat process into anolyte

We are having problems with anolyte for a electrocoating application. The colour of the anolyte (acetic acid ⇦this on eBay or Amazon [affil links] ) has changed from a normal pale yellow to a dark red/black colour. It is suspected that the 316 stainless steel anodes may be "dissolving" as high concentrations of Cr, Ni and Mo are found in the anolyte solution. A change of voltage has been tested through the anodes recently, could this be the source of the problem? Any other theories on the topic?

Mark O'Connor
- Adelaide, SA, Australia
2002

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Dear Sir,

You are correct, the anodes are dissolving. This is typical for this application. The stainless steel anode is considered soluble and will dissolve over time. The color change is due to the dissolved iron from the anode going into solution at it dissolves. This can make it necessary to increase the voltage to get the same current draw. This is due to the fact that the iron is a cation and is being drawn to the cathode(part)but the membrane is in between and the iron plates out on the inside of the membrane increasing the resistance.

Eric Legatski
- Fayetteville, North Carolina
2003