利用电子散斑干涉技术研究45碳钢在NaHCO3-NaCl体系中的早期点蚀行为

MONITORING INITIAL PITTING CORROSION OF 45 STEEL IN NaHCO_3-NaCl SOLUTION BY ESPI

首次利用电子散斑干涉法(ESPI)实时和原位检测了45碳钢在0.5 mol/L NaHCO_3+0.05 mol/L NaCl体系中阳极极化时的局部腐蚀行为.研究发现,电子散斑干涉图上的亮斑与电极表面蚀点一一对应,从电子散斑干涉图中亮斑出现的情况可以推测出45碳钢表面发生早期点蚀的时间、大小和位置。测量得到本实验条件下45碳钢的点蚀电位E_b为-0.15 V,此时的极化电流为12.2μA.通过分析激光电子散斑干涉图中的亮斑变化情况,可以获得电极表面蚀点生长信息。

ESPI were firstly used to monitor the real-time, in-situ corrosion behavior of 45 steel in 0.5 mol/L NaHCO3＋0.05 mol/L NaCl solution during anodic polarization. By comparison between the ESPI image and the digital photo of the sample surface; it was found that at the same position where a speckle appeared, a pit appeared after the polarization experiment. It can be concluded that the bright speckles in the ESPI images were caused by the pitting corrosion products. Accordingly, the size, position and time of initial pitting corrosion could be deduced. The pitting potential （Eb） of 45 steel determined by the method under the condition is -0.15 V; meanwhile, the polarization current is 12.2μA. Information of the pitting growth could be obtained by changes of the speckles in ESPI results.