X70钢及其焊缝在Na_2CO_3+NaHCO_3溶液中电化学腐蚀行为研究

Electrochemical Corrosion Behavior of Matrix and Weld Seam of X70 Steel in Na_2CO_3+NaHCO_3 Solutions

采用动电位极化、电化学阻抗谱和Mott-Schottky方法研究了溶液浓度和Cl^-对X70钢母材及其焊缝在Na_2CO_3+NaHCO_3溶液中电化学腐蚀行为影响。结果表明,X70钢母材和焊缝在0.1~1.0 mol/L(Na_2CO_3+NaHCO_3)溶液中都能形成稳定的钝化区间。随着溶液浓度的增大,钝化膜的稳定性增加。X70管线钢母材和焊缝的钝化膜均呈现出n型半导体特征,且施主密度与维钝电流密度的变化趋势相同。Cl^-在1.0 mol/L(Na_2CO_3+NaHCO_3)溶液中,对焊缝组织的吸附现象存在显著特征,主要吸附于氧空位处。

The electrochemical corrosion behavior of the matrix and weld seam of X70 steel in Na2CO3＋NaHCO3 solution was studied by means of potentiodynamic polarization, electrochemical imped- ance spectroscopy and Mott-Schottky technique. Results showed that the passive film could form on both the matrix and weld seam of X70 steel in solutions with the concentration of Na2CO3＋NaHCO3 within a range of 0.1-1.0 mol/L. The stability of passive films increased with the concentration of Na2CO3＋NaHCO3. The passive films form on both the matrix and weld seam of X70 steel behave as a n-type semiconduc- tor, the donor density follows the same trend as the passivity current density. There is a notable feature that the CI- adsorbed onto the oxygen vacancies on the weld seam in the solution of 1 mol/L carbonate/bi- carbonate.