硝酸钝化对304不锈钢在模拟混凝土孔隙液中点蚀的临界Cl-浓度的影响

Effect of Nitric Acid Passivation on Critical Cl Concentration for Corrosion of 304 Stainless Steel in Simulated Concrete Pore Solution

通过动电位极化曲线、电化学阻抗谱以及Mott-Schottky测试研究了经硝酸钝化后的304不锈钢在模拟混凝土孔隙液中的耐蚀性。结果表明,硝酸钝化提高了304不锈钢在模拟混凝土孔隙液中点蚀的临界Cl^(-)浓度,未钝化处理及钝化0.5,2和24 h的临界Cl^(-)浓度分别为0.05~0.1,4~5,2~4和1~2 mol/L。Mott-Schottky测试结果表明,经硝酸钝化处理后304不锈钢的钝化膜载流子密度减小,膜稳定性增加,耐蚀性提高。

The corrosion resistance of 304 stainless steel passivated by nitric acid in simulated concrete pore solutions was studied through the polarization curves, electrochemical impedance spectroscopy(EIS) and Mott-Schottky measurement. The results indicate that the critical Cl^(-) concentration for the corrosion of 304 stainless steel in the simulated concrete pore solution was increased after nitric acid passivation. The bare steel and the steel subjected to passivation treatment for 0.5, 2 and 24 h presented different range of critical chloride ion concentrations, namely 0.05~0.1, 4~5, 2~4 and 1~2 mol/L, respectively. The Mott-Schottky test results show that the nitric acid passivation treatment reduces the carrier density of the passivation film and increases the stability of the film. The EIS measurement by potentiostatic polarization is suitable for detecting the critical Cl^(-) concentration.