Electropolishing is an electrochemical surface finishing process, often described as reverse electroplating. Unlike electroplating that adds metal coating onto workpieces, it removes a controlled, ultra-thin layer of metal from the component surface through anodic dissolution. The metal part acts as the anode and connects to the positive pole of a DC power supply, while an inert cathode is immersed together with the part in a temperature-stabilized electrolyte bath, mostly a mixed solution of phosphoric acid and sulfuric acid for stainless steel.

The core polishing mechanism relies on selective material removal. When direct current passes through the electrolyte, electric field strength concentrates at microscopic peaks, sharp edges and tiny burrs on the metal surface. These raised points dissolve much faster than surface valleys. A viscous diffusion film forms on the workpiece surface during reaction; this film is thinner at peaks, which accelerates ion exchange and further speeds up dissolution of high spots. Gradually, the rough surface is leveled into a smooth, bright, non-directional finish.

Key process parameters must be strictly controlled for stable quality: current density, electrolyte temperature, processing time and electrolyte concentration. Even minor changes will alter material removal rate and final roughness. Normally, only several microns of metal are removed, so electropolishing cannot fix large machining defects or heavy geometric errors. It only optimizes micro-scale surface features.

This process is widely used for stainless steel, titanium, copper and aluminium. Besides brightening appearance, it eliminates embedded free iron, machining debris and micro-cracks left by CNC turning, milling or stamping. A chromium-rich passive layer forms naturally on stainless steel after polishing, greatly lifting corrosion resistance. As a non-contact method, it introduces no mechanical stress, scratches or deformation. It is especially suitable for complex parts with internal cavities, narrow grooves and irregular outlines that mechanical polishing cannot reach. For precision manufacturing, electropolishing serves as a reliable micro-finishing solution to meet strict cleanliness and surface specification requirements.