Effect of nitrogen on corrosion resistance of stainless steel

　　1. Influence on the microstructure of stainless steel

　　The effect of nitrogen on stainless steel is very strong. The nitrogen element in the stainless steel matrix can replace part of the nickel element, reduce the ferrite content in the stainless steel, help stabilize the austenite, reduce the precipitation of harmful intermetallic phases, and even eliminate the martensite transformation during cold working.

　　2. Influence on mechanical properties of stainless steel

　　The effect of nitrogen on the mechanical properties of the matrix in stainless steel is mainly reflected in two aspects. First of all, nitrogen can significantly increase the strength of stainless steel, and will not reduce the plastic toughness of stainless steel. This is a good study of the direction of high strength and toughness of stainless steel. Secondly, the nitrogen element can also enhance the creep resistance, fatigue resistance and wear resistance of the stainless steel.

　　3. Influence on corrosion resistance of stainless steel

　　Nitrogen is also beneficial for increasing the corrosion resistance of stainless steel. Mainly to improve the resistance to intergranular corrosion, pitting corrosion, crevice corrosion. The mechanism of nitrogen resistance to pitting corrosion and crevice corrosion of stainless steel is mainly acid consumption theory. Nitrogen forms NH4+, lowers pH value, prevents anode dissolution and slows local acidification, which can inhibit the autocatalytic process of pitting corrosion. Secondly, the enrichment of interfacial nitrogen, the enrichment of nitrogen in the passivation film of the metal interface near the metal side, will affect the repassivation kinetics, promote the rapid re-passivation of the stainless steel surface, and thus play a role in suppressing pitting corrosion. In addition, nitrogen and other elements can work synergistically. Nitrogen can inhibit the over-passivation and dissolution of elements such as chromium and molybdenum, and can produce a stronger surface layer in the local corrosion process of the stainless steel plate surface, and improve the corrosion resistance of the stainless steel plate surface.

　　Nitrogen plays an indispensable role in the stability and corrosion resistance of stainless steel, and since nitrogen is cheaper than alloying elements such as nickel and chromium, the future development space in the field of stainless steel should have unlimited potential.

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