关键词: 碳钢, 电流波动, 亚稳态孔蚀

Abstract: The characteristics of current fluctuations of A3 carbon steel in NaNO2_NaCl solutions were studied with potentiostatic and potentiodynamic polarization methods. The steel remained stable passivation in 0.1 mol/L NaNO2 solution without Cl-. After NaCl was added in to the solution, current fluctuations with a characteristic of quick increase and slow decrease occurred, indicating quick dissolution and slow re_passivation of the metastable pits. The metastable pitting may cause accumulated corrosion damage around certain area and result in observable pits. With the increase of chloride concentration, the occurring potential for metastable pits Em rised, and peak values and frequency of current fluctuations also rised. The increase in potentials led to increase of peak values, frequency and decay time of urrent fluctuations, which implies that higher potential promotes both nucleation and dissolution of metastable pits.