基于声发射的储罐底板钢点蚀特征

The pitting corrosion characteristics of tank bottom plate steel based on acoustic emission technology

储罐罐底腐蚀乃至穿孔事故严重威胁了储罐的运行安全。联合采用声发射和电化学技术研究了常压储罐底板Q235钢试样在质量分数为3%、pH值为2的酸性氯化钠溶液中的点蚀行为,分析了点蚀过程中各阶段产生声发射信号的幅度、能量、撞击数、持续时间、上升时间等特性参数随时间的分布,以及多个特性参数之间的相互关联,同时将声发射监测结果与电化学极化结果进行对比。结果表明:底板钢点蚀阶段声发射监测结果与电化学极化结果具有一致性,氧化膜的剥离和破裂、蚀坑的形成和扩展、腐蚀产物层间的摩擦和开裂行为产生的声发射信号特征具有明显差异,研究结果对评估常压金属储罐罐底声发射在线检测结果,判断腐蚀程度,鉴别腐蚀类型具有一定的指导意义。

The corrosion and even perforation of tank bottom have seriously threatened the operation safety of tanks. In this paper, the pitting corrosion behaviour of the specimens of Q235 plate steel used for atmospheric storage tank bottom in acidic NaCl solution(mass fraction is 3%, pH is 2) was studied by acoustic emission(AE) and electrochemical technologies. The distribution of characteristic parameters of AE signal(including amplitude, energy, hits, duration time and rise time) over the time in each stage of pitting corrosion, and the relationships among them were analyzed. In addition, the AE monitoring results were compared with the electrochemical polarization results. It is shown that the AE monitoring results are consistent with the electrochemical polarization results during the pitting corrosion of bottom plate steel, the AE signal characteristics are remarkably different in the exfoliation and rupture of oxide film, the formation and propagation of corrosion pit, the friction between corrosion products and the cracking behaviour, and the extraction of these characteristics is helpful for assessing the AE on-line detection results of the bottom of atmospheric metal storage tank, diagnosing the corrosion degree and identifying the corrosion type.