Effect of nitrogen element on corrosion resistance of stainless steel

　　The role of nitrogen in stainless steel

　　1.Effect on the stainless steel matrix structure

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

　　2.Effects on the mechanical properties of stainless steel

　　The effect of nitrogen in stainless steel on the mechanical properties of the matrix is mainly reflected in two aspects. First of all, nitrogen can obviously improve the strength of stainless steel without reducing the plastic toughness of stainless steel. This is a good direction to study the high strength and toughness of stainless steel. Secondly, the nitrogen element can also enhance the creep resistance, fatigue resistance and wear resistance of stainless steel.

　　3.Effect on the corrosion resistance of stainless steel

　　Nitrogen is also good for increasing the corrosion resistance of stainless steel. It mainly reflects the improvement of resistance to intergranular corrosion, pitting corrosion and crevice corrosion. The action mechanism of nitrogen on pitting and crevice corrosion resistance of stainless steel is mainly the acid consumption theory. Nitrogen forms NH4 +, lowers the pH value, prevents the anode from dissolving, and slows local acidification, which can inhibit the autocatalytic process of pitting. The second is the enrichment of nitrogen at the interface. The enrichment of nitrogen in the metal interface passivation film near the metal side will affect the repassivation kinetics, promote the rapid repassivation of the stainless steel surface, and play a role in inhibiting pitting corrosion. In addition, nitrogen and other elements can play a synergistic role. Nitrogen can inhibit the overpassivation and dissolution of chromium, molybdenum and other elements, and can produce a more resistant surface layer during the local corrosion of the stainless steel plate surface, improving the corrosion resistance of the stainless steel plate surface. .

　　From the above, we can know that nitrogen element plays an indispensable role in the stability and corrosion resistance of stainless steel, and because nitrogen element is cheaper than alloy elements such as nickel and chromium, the future development potential in the stainless steel field is great.

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