Electropolishing and Passivating

Electropolishing involves passage of electric current through a workpiece, while it is submerged in a specially-designed acid solution. The process is essentially the reverse of electroplating, in that the surface of the workpiece is actually “stripped away.” When used on stainless steel, the process removes iron and nickel (as well as non metallics) from the surface, thus enhancing the chromium content and corrosion resistance of the workpiece surface.

The amount of surface material removed can be precisely controlled by voltage, current, time and temperature. Electropolishing also has the added benefit of attacking the “high points” of the surface of the workpiece more aggressively, resulting in a smoothing, or polishing of the surface. In many cases such as medical, food and beverage, and semiconductor products, this smoothing of the surface reduces the microscopic crevices in which bacteria can propagate and tiny particles can accumulate, thus aiding sterilization and cleaning processes.

The removal of metallic and non-metallic particles, that are often added to the surface by cutting and forming processes, also results in a superior surface for welding. This reduction of impurities reduces he presence of crack forming inclusions that can compromise weld strength.

The diagram shows a typical electropolishing process. The workpiece is mounted on special racks of either copper or titanium. The rack, along with the workpiece, is submerged into an acid solution (held at a specific temperature), and current is passed from the anode (workpiece), through the acid solution, and into the cathode (lead). The surface of the workpiece is literally “dissolved” away, leaving an extremely clean and polished surface on the workpiece.