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I have been experimenting with electrolysis for producing oxyhydrogen and using potassium carbonate as an electrolyte. After several hours of electrolysis, I notice the plates began to tarnish and after 24 hours, are now dark brown. The plates are made of 316 stainless steel and the electrolyte remains clear.

When I chose to use K2CO3; I thought that it would not decompose during electrolysis but now I suspect that it is decomposing and electroplating the stainless steel plates with carbon. If this is the case; will this have an adverse effect on the plates ability to conduct and produce oxyhydrogen? Also, is CO2 being produced?

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Since the carbonate radical is covalently bonded, it probably is not being decomposed electrolytically. Much more likely is that iron in the stainless steel is being removed and oxidized, leaving a thin film of "rust" on the plates.

A few ways you can prove this:

  1. Immerse the browned plates in oxalic acid, which will slowly dissolve iron oxides, but leave carbon untouched.

  2. Substitute platinum electrodes -- admittedly expensive, but Pt is the "gold" standard for electrodes. They should not discolor.

  3. Spray the browned plates with a solution of potassium ferricyanide. If free iron is present, a blue color ("Prussian blue") appear.

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