Principle And Classification of Chemical Polishing

Chemical polishing is a method of removing wear scars and etching leveling by the selective dissolution of chemical reagents on the uneven areas of the product surface. It is a chemical treatment method of immersing metal parts in acidic or alkaline solutions in order to improve the surface roughness of metal parts. Chemical polishing can rely on the spontaneous chemical reaction of the chemical polishing liquid to automatically improve the surface finish of the work-piece to be polished without the help of electricity and manpower, which can achieve a mirror effect. It can be also simply understood: chemical polishing is the use of chemical potions to brighten the products.

Principle of Chemical Polishing

The principle of chemical polishing is that the metal surface is bright and smooth through regular dissolution. In the chemical polishing process, the passive oxide film and the oxide film are continuously formed on the surface of the metal parts, and the former is stronger than the latter. Due to the microscopic inconsistency of the surface of the parts, the surface microscopic convex parts are preferentially dissolved, and the dissolution rate is greater than the dissolution rate of the concave parts. And the dissolution of the film and the formation of the film always proceed at the same time, but the rate is different, resulting in the surface roughness of the metal part is leveled to obtain a smooth and shiny surface. Chemical polishing can fill surface pores, scratches and other surface defects, thereby improving fatigue resistance and corrosion resistance.

Classification of Chemical Polishing

There are three types of chemical polishing in terms of main components.

– The earliest one is three acid polishing. The main components are sulfuric acid, nitric acid and hydrochloric acid, nitrogen oxides are generated during the reaction.

– The second process is chromate polishing. Due to the strong oxidation of chromate, no chemical fumes can be achieved.

– The last process is hydrogen peroxide polishing. The main products of the reaction are water and hydrogen.