Fe-Ni基合金在热浓碱溶液中的阳极溶解与钝化行为

采用快速与慢速动电位扫描法研究了Fe-Ni基合金在含与不含杂质的沸腾50%NaOH溶液中的阳极溶解与钝化行为.Cr、Ni对Fe-Ni基合金低电位钝化起主要作用,高电位钝化主要是Fe与Ni的作用.Na2S2O3对碱性溶液中元素Fe与Ni的阳极溶解有明显的促进作用,并加速Fe-Ni基合金的溶解导致多处新的阳极电流峰出现.Fe-Ni基合金在相同介质条件下快速扫描的电流密度值比慢扫的大,并对快、慢扫描极化曲线计算出SCC的指数值与SCC行为进行了相关分析.

ANODIC DISSOLUTION AND PASSIYATION OF AN Fe-Ni BASE ALLOY IN HOT CONCENTRATED CAUSTIC SOLUTIONS

The anodic dissolution and passivation of an Fe-Ni base alloy in boiling 50%(wt) sodium hydroxide solution with or without impurities were studied by potentiodynamic polarization curves with fast and slow scan rates. The passivation of the alloy at lower potentials was mainly contributed by Cr and Ni, while the passivation at higher potentials was mainly contributed by Ni. Sodium thiosulfate significantly accelerated the anodic dissolution of Ni and Fe and thus caused some new anodic current peaks by enhancing the dissolution of alloy. The current density obtained with fast scan rate was higher than that with slow scan rate. The correlation of stress corrosion cracking behavior to the parameter SCC index Pi which is calculated from current densities from both fast and slow scans is discussed.