醋酸介质中T-403塔不锈钢填料腐蚀机理研究

某化工厂PTA装置氧化单元系统中铁离子含量增高，已影响到氧化反应效果，严重威胁稳定生产，分析认为铁离子主要来自T-403溶剂回收塔316L不锈钢填料的腐蚀．利用扫描电镜、电子探针、金相显微镜等现代物理和化学分析检测手段，观察了从T-403塔取出填料的微观形貌，测试分析了所用填料的主要化学成分及元素分布，对比了未使用和已腐蚀填料的金相显微结构、力学性能变化，研究分析了不锈钢填料的腐蚀机理．实验结果表明：不锈钢填料发生了严重的局部腐蚀，腐蚀形态为晶间腐蚀和小孔腐蚀．填料发生腐蚀后，强度和硬度明显降低．测试分析结果证明，贫铬导致晶间腐蚀，Br以及不锈钢钝化膜局部破损造成蚀孔．原填料质量存在问题，不锈钢填料的含碳量未达到超低碳316L不锈钢的标准．

Research on corrosion mechanism of stainless steel stuffing in T-403 tower in acetic acid solution

In the oxidation unit system of the PTA device of a chemical plant, the content of iron ion increased. The increased iron ion has already influenced the result of oxidation reaction, threatened the steady production seriously. Analytical results show that the iron ion mainly comes from the corrosion of 316L stainless steel packing of T-403 solvent recovery tower. By some modern physical detective technologies and chemical analysis methods as scanning electron microscopy, electronic probes, metallurgical analysis, the corrosion profiles, chemical composition and element distribution of stuffing from T-403 tower were observed. Metallurgical structures and mechanics properties were compared in stainless steel using and without using stuffing. Corrosion mechanism of stainless steel stuffing was researched. The test result shows that relatively serious local corrosion has happened in the stuffing sample. The characteristic is intergranular corrosion and pitting. After the packing is corroded, the tensile strength and rigidity are all obviously reduced. Intergranular corrosion arises from the lack of chromium. While pitting was caused by the damage of local passivation film and Br~- in acetic acid solution.The original packing material has the problem of quality, the carbon content of the stainless steel packing has not reached the standard of the ultralow carbon 316L stainless steel.