The coating materials (resins, pigments, additives, etc.) are dispersed in water and held in a bath. The parts to be coated are immersed in the solution and an electrical current is passed through the bath using the parts as an electrode.
Electrical activity around the surface of the parts makes the resin directly in contact become insoluble in water. This causes a layer of resin including any pigments and additives present to adhere to the surface of the parts. The coated parts can then be removed from the bath and the coating is normally cured by baking in an oven to make it hard and durable.