SUS316L 系ステンレス鋼の局部腐食挙動に及ぼす窒素添加の影響

概要

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The effect of nitrogen addition up to 0.556 mass% on corrosion behavior in SUS316L type austenitic stainless steels was examined, where a particular emphasis was put on chemical analysis of an anolyte by the macro-cell method. It is found that the pitting potential becomes higher with an increase in nitrogen content. The critical pitting temperature is elevated by nitrogen addition and well summarized by using the pitting index of Cr+3Mo+26N (mass%). From the analysis of the anolyte cell solution by the galvanostatic electrolysis with macro-cell instrumentation, NO_3^- is detected only in nitrogen bearing steels when the potential is kept at a higher level, while NH_4^+ is detected in nitrogen free steels and in nitrogen bearing steels when the potential is lowered. The potential-pH equilibrium diagram for nitrogen-water system shows that NH_4^+ is stabilized at lower potentials and NO_3^- is done at higher potentials. It is believed that NO_3^- acts as a powerful inhibitor against Cl^- attack to the passive film while NH_4^+ raises pH in a corrosion pit so as to suppress the localized corrosion.
社団法人日本鉄鋼協会の論文
1998-07-01