Electro-Polishing VS Chemical Polishing

Electrolytic polishing refers to the anodic oxidation of metal products in a solution of a specific ratio to obtain a smooth, shiny surface. The metal parts are immersed in an electrolytic bath, and direct current is utilized to produce selective anodic dissolution, which reduces the microscopic roughness of the metal surface and achieves the effect of increasing the surface brightness of the workpiece. Electrolytic polishing can also be the surface preparation before plating and the finishing of the metal surface after plating. Electrochemical polishing is suitable for non-ferrous metals and other single-phase alloys with low hardness, such as aluminum alloys, austenitic stainless steel, high manganese steel, etc., but it is not applicable to metallographic samples of metals with inhomogeneous chemical compositions and inhomogeneous shapes. Serious microscopic segregation and non-metallic inclusions exist in the metal matrix.

Electrochemical polishing can be used on many occasions to replace complex mechanical polishing, especially for parts with complex shapes that are difficult to process mechanically. Electrochemical polishing has the advantages of long-lasting luster, high efficiency and low cost. However, electrochemical polishing also has its defects, such as can not remove or cover the deeper scratches and other surface defects, also can not remove non-metallic inclusions in the metal. In multiphase alloys, if one of the phases is not easily dissolved by the anode, it will affect the quality of electrolytic polishing. This depends on the current density, and the metallographic structure depends on the original surface, temperature and agitation.

Chemical polishing is another common finishing process for metal surfaces. It chemically etches metal parts in a specific solution in a process where the metal surface is etched and leveled by the solution to obtain a brighter surface. Chemical polishing can be used for surface finishing of parts such as instruments, aluminum reflectors or plating for decorative treatment. Compared with electrolytic polishing, the advantages of chemical polishing are: no external power supply, can handle parts with more complex shapes, high production efficiency, but the surface quality of chemical polishing is generally slightly lower than that of electrolytic polishing, its preparation and regeneration of its solution is more difficult, and often precipitate nitrogen oxides and other hazardous gases, seriously polluting the environment.