1. There are four methods for polishing duplex stainless steel flanges: manual, mechanical, chemical, and electrochemical. Polishing improves the flange's corrosion resistance and aesthetics. Existing electropolishing solutions for stainless steel still use phosphoric acid and chromic anhydride; during polishing and cleaning, some chromium and phosphorus enter wastewater, polluting the environment.

　　2. A passivation film forms on the surface of the duplex stainless steel flange, and simultaneously, the oxide film begins to dissolve. Due to the microscopic inconsistencies on the surface of the duplex stainless steel flange, the slightly convex parts dissolve preferentially, and the dissolution rate is greater than that of the concave parts. Film dissolution and formation occur almost simultaneously, but at different rates. The result is a reduction in the surface roughness of the duplex stainless steel flange, resulting in a smooth, glossy surface.

　　3. Polishing fills surface pores and scratches, improving fatigue resistance and corrosion resistance. Duplex stainless steel flanges have more than twice the yield strength of austenitic stainless steel, sufficient formability, and superior resistance to stress corrosion cracking, especially in chloride environments.