The use of insoluble anodes in trivalent chromium plating solutions causes build up of free acid and formation of Cr(YI), resulting in the deterioration of chromium coatings. Concentration of sulfate ions gradually increases as a result of periodic replenishment of chromium content by adding chromium sulfate to the solution. Ion-selective membranes were used in the current study for the separation of insoluble anodes from the plating solution. An appropriate combination of the membrane type and the anolyte allows the avoidance of anodic oxidation of Cr(III) to Cr(YI) and Cr(II) to Cr(III), increasing the current efficiency of chromium metal and maintaining a constant pH without additions of acids or alkalies, as well as maintaining a constant concentration of sulfate ions.
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