用电化学噪声技术研究Q235钢在含氯盐模拟混凝土孔隙液中的腐蚀行为

采用电化学噪声技术(EN)和电化学阻抗谱(EIS)研究了Q235钢在0.5 mol/L NaCl的饱和Ca(OH)₂溶液(SCP)中的腐蚀过程，并对噪声数据进行时域分析与频域分析，对阻抗谱数据进行等效电路分析。采用SEM结合EDS和XRD研究了Q235钢的表面形貌和结构组成。结果表明，Q235钢在SCP溶液中的腐蚀过程可分为钝化膜的形成与破裂阶段(Ⅰ)、亚稳态点蚀阶段(Ⅱ)和Ca²⁺沉积和腐蚀产物形成阶段(Ⅲ)。在(Ⅰ)阶段，电流噪声的波动幅值较小，电流噪声标准偏差S_I、白噪声水平W_I较小、噪声电阻R_n较大；在(Ⅱ)阶段，电流噪声波动幅值较大，S_I、W_I呈现阶跃式增长，R_n显著降低；在(Ⅲ)阶段，电流噪声波动幅值增大到200 nA，S_I、W_I、R_n平稳波动。Q235钢在SCP溶液中腐蚀10 d后在其表面出现Fe₂O₃和弥散分布的CaCO₃晶体，此时阻抗谱中出现类Warburg阻抗，腐蚀反应受电荷转移和O₂扩散的联合控制。

Assessment on Corrosion Behavior of Q235 Steel in a Simulated Concrete Pore Liquid Containing Chloride by Electrochemical Noise

The corrosion process of Q235 steel in 0.5 mol/L NaCl saturated Ca(OH)₂ solution (SCP) was investigated by electrochemical noise technology (EN) and electrochemical impedance spectroscopy (EIS), and the noise data were analyzed in time domain analysis and frequency domain analysis, and the impedance spectrum data were analyzed by way of equivalent circuit. The surface morphology and structure of the tested Q235 steel were characterized by SEM combined with EDS and XRD. The results show that the corrosion process of Q235 steel in SCP solution can be differentiated into three stages: (Ⅰ) the formation and cracking stage of passivation film, (Ⅱ) the metastable pitting corrosion stage and (Ⅲ) the Ca²⁺ deposition and corrosion product formation stage. In the stage (I), the amplitude of current noise fluctuation, the current noise standard deviation S_I and the white noise level W_I are relatively small, but the noise resistance R_n is relatively large; In the stage (Ⅱ), the amplitude of current noise fluctuation is large, S_I and W_I show a step-wise increase, and R_n decreases significantly; In the stage (Ⅲ), the amplitude of current noise fluctuation increases to 200nA, and S_I, W_I, R_n fluctuate relatively smoothly. When Q235 steel is corroded in SCP solution for 10 days, Fe₂O₃ with dispersed CaCO₃ crystallites can be observed on the surface of Q235 steel. At this time Warburg impedance appears, while the corrosion reaction is jointly controlled by the charge transfer and O₂ diffusion process.