NO_2^-及其浓度对混凝土模拟孔隙液中碳钢早期孔蚀的作用

Inhibition Effect of NO_2^- and Its Concentration on Metastable Pitting Corrosion of Carbon Steel in a Simulated Concrete Pore Solution

应用动电位极化、Mott-Schottky曲线测试和XPS测试等方法研究了含0.05 mol/L Cl-,p H值为11的混凝土模拟孔隙液中常用缓蚀剂亚硝酸盐对Q235碳钢小孔腐蚀早期行为的影响。结果显示,NO2-对稳定孔蚀和亚稳态孔蚀均有很好的抑制作用,亚稳态孔蚀电位和稳定孔蚀电位均随着NO2-浓度的增加而增大,且影响趋势接近。NO2-浓度较低时,对孔蚀的抑制作用很明显,超过0.03 mol/L后抑制作用变化不大。这是因为,NO2-浓度增大,钝化膜中更多的Fe2+被氧化为Fe3+,膜中的氧空位缺陷浓度降低,因此小孔的形核受到抑制。

The Effect of NO2-on the early stages of pitting corrosion of Q235 carbon steel in a simulated concrete pore solution(p H=11) was studied by means of polarization curves, Mott-Schottky curves and XPS methods. It was found that, NO2-inhibits both the stable pitting corrosion and the metastable pitting corrosion. The metastable pitting corrosion potential and the stable pitting corrosion potential increase with the increase of NO2-concentration and follow the similar trend. The nucleation process of pits can apparently be inhibited by a low content of NO2-, however this effect increases only slightly as the NO2-content higher than a critical value about 0.03 mol/L. With the increase of NO2-concentration, more Fe2 +in the passive film can be oxidized into Fe3 +and thereby,the defect density related with oxygen vacancies decreases, so the nucleation process of pits may be inhibited.