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针对油轮货油舱底部的高氯离子强酸性腐蚀环境,参照了IMO《货油舱用耐蚀钢实验程序》的要求,深入研究了腐蚀溶液的pH值对其腐蚀特性的影响,对比分析了普通E36级船板钢以及等强度级别的耐蚀船板钢腐蚀行为的差异。研究结果表明,pH值对钢的腐蚀速率有显著影响。pH<3.0时,耐蚀钢的耐腐蚀性能,尤其是耐点蚀性能明显优于传统钢;pH≥3.0时,耐蚀钢和传统钢的腐蚀速率未表现出明显差异。强酸性氯离子环境下,实验钢的纯净度、微量耐蚀合金设计、显微组织共同决定了其耐腐蚀性能。钢中的非金属夹杂物是诱发局部腐蚀的主要原因;Cu、Ni、Sn元素的复合添加能显著提高耐蚀钢的腐蚀电位,同时耐蚀合金元素在锈层内部富集,提高了耐蚀钢表面锈层的致密性与稳定性;单一均匀的贝氏体显微组织有利于提高实验钢在酸性氯离子环境下的耐蚀性能,这主要是由于贝氏体组织中富碳相较少且分布均匀。
According to the requirements of IMO “Corrosion-Resistant Steel for Cargo Tank”, the influence of pH value of corrosion solution on the corrosion property of high-chloride ion corrosive environment at the bottom of tanker is analyzed. The difference of corrosion behavior of common E36 grade shipboard steel and other strength grade corrosion resistant shipboard steels. The results show that pH has a significant effect on the corrosion rate of steel. The corrosion resistance of corrosion-resistant steel, especially the pitting corrosion resistance is obviously better than that of the traditional steel when the pH is less than 3.0. However, the corrosion rate of the corrosion-resistant steel and the traditional steel does not show obvious difference when pH≥3.0. Strong acid chloride environment, the purity of experimental steel, micro-corrosion-resistant alloy design, microstructure determine its corrosion resistance. Non-metallic inclusions in steel are the main causes of local corrosion. The composite addition of Cu, Ni and Sn can significantly increase the corrosion potential of corrosion-resistant steel, meanwhile, corrosion-resistant alloying elements are enriched in the rust layer to improve corrosion resistance Steel surface rust layer density and stability; a single homogeneous bainitic microstructure is conducive to improve the corrosion resistance of experimental steel in acid chloride environment, mainly due to the bainitic tissue less carbon-rich and evenly distributed.