【摘要】 通过电化学噪声(ECN)、电化学阻抗(EIS)及极化曲线研究了四乙烯五胺(TEPA)在碳化模拟混凝土孔隙液中对Q345B碳钢点蚀的抑制机理.结果表明:通过吸附成膜和隔离Cl-离子对钝化膜的侵蚀,TEPA浓度升高导致碳钢点蚀电位正移.低浓度的TEPA会造成亚稳态蚀点形核速率略微增加,但会降低其寿命.随着TEPA浓度增加,噪声电阻上升,而亚稳态蚀点寿命和平均点蚀电量则迅速下降,表明其明显加速了亚稳态蚀点修复,当TEPA浓度达0.10mo·lL-1时,噪声峰消失,基底电流趋于零,蚀点全面钝化.TEPA不仅能抑制Cl-离子引起的亚稳态和稳态蚀点生长,还可吸附于钝化膜表面,抑制膜的均匀溶解.形貌观察表明,亚稳态蚀点主要在稳态蚀点周围形核和生长,并不断为稳态蚀点所吞并,造成碳钢表面蚀坑一般沿平面而不是垂直方式扩展.更多还原

【Abstract】 Tetraethylenepentamine (TEPA) was surveyed to show strong inhibition on pitting corrosion of Q345B carbon steel in a carbonated synthetic pore solution (SPS) by electrochemical noise (ECN), electrochemical impedance spectroscopy (EIS), and polarization curves. The pitting corrosion potential shifts positively with an increase in the TEPA concentration. ECN data show that the low content of TEPA can increase the nucleation rate of the metastable pits slightly and can effectively reduce their lifespan. The high content (0.10 mol·L-1) of TEPA accelerates the repassivation of metastable pitting and this is accompanied by an increase in noise resistance and a decrease in the nucleation rate and average pitting charge until the noise current transients disappear completely. Both the baseline current and the amplitude of the current transients decrease with an increase in the TEPA concentration, indicating that TEPA retards not only the pitting corrosion but also the general dissolution of the passive film. Micrographs show that the metastable pits mainly initiate and develop around the stable pits because of the induction of corrosion products, which causes the pitting cavity on carbon steel to grow generally in a planar rather than in a perpendicular direction.更多还原