electropolishing

Electropolishing is an electrochemical finishing process where a metal workpiece is made the anode in an electrolytic bath. Material is dissolved from the surface at a controlled rate, yielding a smooth, bright, uniform finish and often improving corrosion resistance compared with mechanical polishing.

During electropolishing, peaks dissolve more rapidly than valleys as current concentrates at microscopic points. The result is a smoother, more homogeneous surface. Common electrolytes are acidic: sulfuric–phosphoric baths for stainless steels and phosphoric-acid–based solutions for aluminum alloys. A cathode completes the circuit, with temperature, agitation, and current density tightly regulated.

Materials typically electropolished include stainless steels, aluminum and its alloys, nickel alloys, titanium, and copper alloys. Finishes are smoother and brighter, with some material removal from the surface that can affect near-surface composition or passivation.

Applications include surgical instruments, medical implants, food-processing equipment, and aerospace or automotive components that require high-quality finishes. Electropolishing can improve reflectivity, ease of decontamination, and resistance to corrosion initiation, contributing to cleaner, more uniform surfaces.

Limitations include variable effectiveness depending on alloy and geometry, hazards associated with corrosive acids and hydrogen evolution, and the need for appropriate containment, ventilation, protective equipment, and waste treatment.