碳钢在NaHCO_3+NaCl溶液中的亚稳态孔蚀特征

Feature of metastable pitting of carbon steel in NaHCO_3+NaCl solutions

用动电位极化和恒电位极化法研究了A3碳钢在不同浓度NaCl的 0 5mol/LNaHCO3 溶液中亚稳态孔蚀行为。实验发现亚稳态电流波动峰具有快速上升、缓慢下降的特点。亚稳孔出现电位Em 服从正态分布 ,随着Cl-浓度的提高 ,Em 值向负方向移动。亚稳孔的峰频变化规律与电位关系不大。恒电位极化时 ,当电位高于Em 而大大低于孔蚀电位Eb 时 ,电流波动保持一定时间后会最终消失 ,并产生直径为微米级的小蚀孔。当电位接近孔蚀电位时 ,一段时间的电流波动后电流往往迅速上升 。

The metastable pitting behavior of A3 carbon steel in 0 5?mol/L NaHCO 3 solutions containing different concentrations of NaCl were studied with the potentiodynamic and potentiostatic polarization methods. It is found that the current fluctuations of the metastable pitting occurred with a characteristic of quick increase and slow decrease. The occuring potential of the metastable pits E m obeys a normal distribution, and decreases with the increase of the chloride concentration. Potential has no apparent effect on the frequency of fluctuations. In potentiostatic test, when the potential is above E m and far below the pitting breakdown potential E b, the current fluctuations remain for a period then disappear, resulting in the pits with a diameter of microns. When potential is close to E b, the current may finally rise continuously after a certain time of fluctuations, and the metastable pitting is replaced by a stable piting.