オーステナイト系ステンレス鋼の高酸化性イオンを含む硝酸中の耐食性に及ぼす合金元素の影響

概要

論文の詳細を見る
Stainless steel has good corrosion resistance in nitric acid. When the corrosion potential is in transpassive region, however, the resistance tends to be decreased according to the oxidizing environment. In this study, the effects of alloying elements such as Mo, Nb, Ti, Zr, Si, Cr and P were investigated on the corrosion resistance of the austenitic stainless steel in the transpassive region, i.e. 40%HNO_3+0.2 g/1Cr^<6+>. The corrosion of welded joint was also examined. The results are as follows. (1) Si was the most effective element for corrosion resistance improvement in highly oxidizing nitric acid, while Mo, Nb, Ti and Zr were not effective. (2) Si improved the corrosion resistance in highly oxidizing nitric acid solutions containing Cr^<6+> ions by suppressing cathodic reaction and by mitigating the detrimental effect of P segregated intergranularly. (3) The corrosion resistance of high Si steel was inferior to that of low Si steel in pure nitric acid, where the steel is in the passive region. On the other hand, Cr showed reverse effects, i.e., improvement of the corrosion resistance in passive potential region, and little effect in transpassive region. (4) Weld metal of Si-bearing austenitic stainless steel corroded severely due to the formation of the intermetallic compounds and segregation of Ni, Si and Nb.
1989-02-01