Traditional coating methods such as spraying, brushing, etc., are difficult to ensure that products with complex structures can get a complete and comprehensive coating, especially the inner cavity and cracks of the product, etc., because these places are not protected and the product is damaged. The overall service life is reduced. The electrophoretic paint coating can make the cavity, weld, edge and other weak parts of the traditional coating method also obtain good coating protection, so that the overall corrosion resistance of the product is significantly improved, and the final length is greatly extended. The service life of the product is improved, and the grade of the product is improved.