Patent ID: 8617379

Claim:
A method for replenishing sulfate ions in situ in an electropolishing electrolyte solution, the method comprising: positioning a substantially anhydrous electropolishing electrolyte solution in an electropolishing cell; adding a first quantity of at least one sulfate salt to the substantially anhydrous electropolishing electrolyte solution, wherein the at least one sulfate salt is substantially insoluble in the electropolishing electrolyte solution in absence of water; electropolishing a metal article in the substantially anhydrous electropolishing electrolyte solution in the electropolishing cell at a substantially constant electrical current while monitoring voltage across the electropolishing cell, wherein water evolved during the electropolishing process is capable of solubilizing at least a portion of the at least one sulfate salt so as to replenish sulfate ions consumed during the electropolishing; and adding a second quantity of the at least one sulfate salt to the electropolishing electrolyte solution when the voltage exceeds a selected value.