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Stainless steel polishing method

2020-11-13

1. Chemical polishing

Chemical polishing is a commonly used surface treatment process for stainless steel. Compared with the electrochemical polishing process, its biggest advantage is that it does not require a DC power supply and special fixtures. It can polish parts with complex shapes and has high productivity. In terms of functionality, chemical polishing can not only obtain a physically and chemically clean surface, but also remove the mechanical damage layer and stress layer on the surface of stainless steel to obtain a mechanically clean surface, which helps prevent local corrosion of parts and improve Mechanical strength, prolong the service life of parts. Since the patent on chemical polishing of stainless steel was issued in the early 1940s, many formulas have been published so far, but people still find it difficult to apply them in practice. Because there are many varieties of stainless steel, and different grades of stainless steel have different corrosion laws, it is impossible to use the same solution, so there are many types of stainless steel chemical polishing solutions.

The basic composition of chemical polishing solution includes corrosive agent, oxidizer and water. Corrosive agent is the main ingredient, if stainless steel is dissolved in the solution, polishing cannot be performed. Oxidizers and additives can inhibit the process and make the reaction proceed in a direction favorable to polishing. Water regulates the concentration of the solution and facilitates the diffusion of reaction products. Whether the chemical polishing of stainless steel can proceed smoothly depends on the reasonable combination of the above components.

2. Electrolytic polishing

Stainless steel electrolytic polishing is to hang stainless steel products on the anode and perform anode electrolytic processing in the electrolytic polishing solution. Electrolytic polishing is a special anode process. In the entire anode electrolytic polishing process, the surface of stainless steel products undergoes two contradictory processes at the same time, that is, the continuous formation and dissolution of oxide film on the metal surface. However, the conditions for the chemical film formation of the protruding parts and depressions on the surface of stainless steel products to enter the passive state are different, and due to anode dissolution, the concentration of metal salt in the anode area continues to increase, forming a high resistivity consistency on the surface of stainless steel products Mucosal layer. The thickness of the viscous mucosa at the microscopic unevenness of the product surface is different, and the anode microscopic surface current is unevenly distributed. The current density at the microscopic protrusions is high and the dissolution is faster, so that the burrs or microscopic protrusions on the surface of the product are preferentially dissolved to achieve leveling; the current density at the depressions is lower and the dissolution is slower. Due to the different current density distribution, the surface of the product continuously forms and dissolves at different rates. The anode surface undergoes two opposite processes at the same time, film formation and dissolution, and the continuous generation and dissolution of the passive film, so that the surface of the stainless steel product is leveled to achieve a highly smooth and glossy appearance, which satisfies the purpose of polishing and finishing the surface of the stainless steel product.


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