工业纯铁在NaNO_2+NaCl溶液中的亚稳态孔蚀及其腐蚀形貌

Metastable pitting and related morphology of pure iron in NaNO_2 +NaCl solution

用动电位极化法研究了工业纯铁在NaNO2 +NaCl溶液中的电流波动特征 ,探讨了多次极化对亚稳态孔蚀行为的影响。工业纯铁在NaNO2 +NaCl体系中早期的蚀孔由许多连续的、较浅的开放性小孔构成 ,这些蚀孔是亚稳态小孔形核、生长和再钝化的结果 ,小孔优先沿研磨形成的沟槽方向形成。反复多次对工业纯铁试样进行动电位极化 ,其亚稳态小孔的形核数目和峰值电流都逐渐降低 ,Em 和Eb 值升高。在每一次极化过程中小孔形核数目则随电位升高而升高。电流 时间曲线上的电流波动峰与表面的蚀孔形貌有良好的对应关系 ,表明有可能根据电流波动的数量和幅值预测材料表面的腐蚀损伤程度。

The current fluctuation features of pure iron in NaNO 2+NaCl solutions were studied by a potentiodynamic polarization method, and the effects of recycled polarization on the metastable pitting behavior were investigated. It was observed that the pits on the sample surface were composed of many smaller pits which was the results of nucleation, growth and repassivation of metastable pits. The small pits were nucleated following the surface grooves left by polishing. Recycled polarization on the same sample resulted in decrease in the nucleation frequency and peak current of the metastable pits, and increase in E m and E b values. While during each potentiodynamic polarization process the nucleation frequency of metastable pits increased with potential. Good relationship was observed between the number and the electric quantities of the current fluctuations measured and the number and the sizes of the pits observed, which indicates that it is possible to predict the extent of corrosion according to the measured current fluctuations.