摘要
测量了奥氏体不锈钢９０４Ｌ在１４０℃、８５％磷酸溶液中的阳极极化曲线，讨论了不同电位区域内的阳极极化行为，并用交流阻抗法研究了不同电位区域内钝化膜的阻抗行为．在活化－钝化过渡区，阻抗谱的高频部分为容抗弧，在低频出现扩散控制现象．在稳定钝化区；阻抗谱由容抗半圆组成，受表面钝化膜的生长和溶解过程所控制．在该区域内，钝化膜的阻抗值达到最大，弥散系数和膜电容值达到最小，表明所生成的钝化膜的耐蚀性好，致密度高，膜较厚且表面均匀．在过钝化区，高频容抗弧的直径大为减小，说明由于过钝化溶解，膜的耐蚀性大大下降；低频出现两个感抗弧，说明出现了阴离子的吸附．阳极充电曲线和电位衰减曲线的结果表明在稳定钝化区内，膜的组织和成分应该是均匀的；钝化膜的生长电位越高，膜越稳定．综上结果表明奥氏体不锈钢在高温磷酸浓溶液中实施阳极保护具有保护电位范围宽（０．３～０．８Ｖ，ＳＣＥ），钝化膜稳定等优点．磷酸的温度越低，保护效果越明显．
The anodic polarization behaviour of type 904L austenitic stainless steel in 85Wt% H3PO4 at 140℃ was investigated using polarization curves, anodic charge curves, potential decay curves and electrochemical impedance spectra. The anodic polarization curve was characterized by four potential regions, i.e. active dissolution (-0.186～-0.12V vs SCE) reginn, active-passive transition (-0.12-0.2V)region, steady-state passive (0.2-0.9V) region and transpassive (>0.9V) region. In the active-passive transition region, the high frequency hot of impedance was a caparitive loop, and the low frequency limit was a Warburg impedance which indicated diffusion control. In steady-state passive region, the complex impedance plane was a capacitive semicircle indicating that the passinging process was controlled by the growth and dissolution of the film. In this region, the resistance of passive film reached its maximum, and the dispersion coefficient and capacitance reaChed their minima, which demonstrated that the films formed had the best corrosion resistance, the highest density, the thickest layer, and the most homogeneous surface. In the transpassive region, the diameter of high frequency capacitive semicircle sharply reduced, which corresponded to the reduction of corrosion resistance of passive film due to its transpassive dissolution; two inductive semicircles were observed at low frequency range, which indicated the adsorption of anion on the electrode surface. It could be concluded from the results of anodic charge curves and potential decay curves that the passive films formed in the steady-state passive region were homogeneous, and their stability increased with the increase of their growth potentials. The authors also discussed the parameters of anodic protection for 904L in hot concentrated phosphoric acid solution, and suggested the best protection potential range was 0.3-0.8V. The lower the temperature of H3PO4, the better the effect of anodic protection.
出处
《中国腐蚀与防护学报》
CAS
CSCD
1995年第1期7-14,共8页
Journal of Chinese Society For Corrosion and Protection
基金
中国科学院上海冶金研究所青年基金
