Electro-coating is a coating method that utilizes an applied electric field to direct the migration and deposition of pigment and resin particles suspended in the electro-coating bath onto the surface of a substrate, which acts as one of the electrodes. The principle of electro-coating was invented in the late 1930s, but the development of this technology and its industrial application began after 1963. Electro-coating has become a special coating film formation method developed in the last 30 years, which is practically significant for water-based coatings. It has features such as water solubility, non-toxicity, and ease of automatic control, leading to its rapid and widespread application in industries such as automotive, construction materials, hardware, and home appliances.

In electro-coating, the conductive workpiece to be coated is immersed in a diluted, low-concentration electro-coating bath and acts as the cathode (or anode). The corresponding anode (or cathode) of the electro-coating equipment is placed in the bath, and a direct current is applied for a certain period between the two electrodes. Through physicochemical action, the paint is deposited on the workpiece, forming a uniform, water-insoluble coating film.