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针对某公司500万吨/年常减压装置换热器E-502设备在使用过程中发生的腐蚀失效问题,通过金相组织观察、SEM、EDS及XRD分析,研究了换热管的腐蚀失效原因及机理。结果表明:换热管内、外表面均发生了局部腐蚀,且外表面要比内表面腐蚀严重;换热管外表面腐蚀产物中的主要物相有α-FeO(OH)、Fe2O3和Fe3O4,内表面腐蚀产物有大量非晶体,以及少量Fe3O4和Fe2O3;E-502换热器的腐蚀作用主要来源于溶解氧对碳钢的电化学腐蚀及含盐污水中高含量Cl-的吸附、渗入膜内破坏膜的保护性,引起了坑蚀核,在自催化作用下导致孔蚀破坏。
Aiming at the corrosive failure problem occurred in the process of using E-502 heat exchanger for a 5 million ton / year atmospheric and vacuum distillation unit of a company, the corrosion failure of the heat exchange pipe was studied by means of metallographic observation, SEM, EDS and XRD analysis Reasons and mechanism. The results show that both the inner surface and the outer surface of the heat exchange tube have local corrosion and the outer surface is more corroded than the inner surface. The main phase of the corrosion products on the outer surface of the heat exchange tube is α-FeO (OH), Fe2O3 and Fe3O4, Corrosion products have a lot of non-crystal, and a small amount of Fe3O4 and Fe2O3; E-502 heat exchanger corrosion mainly comes from dissolved oxygen on the electrochemical corrosion of carbon steel and salt water containing high levels of Cl- adsorption, infiltration membrane damage film Of the protective nature, causing pit corrosion nuclei, resulting in pitting corrosion under autocatalytic damage.