When purifying by electrolysis, an aqueous sulfate solution at 50 to 70 °C is typically used with a lead anode (corrosion products from which will not contaminate the cobalt oxy-hydroxide (CoOOH) electrolyte solution) and a stainless steel cathode which will allow for the easy removal of the deposited cobalt. Electro refining in a chloride or sulfate medium at −0.3 V will make a cathode coating of 99.98% cobalt.