循环冷却水系统中立式蒸发器腐蚀原因分析

采用化学分析法,扫描电镜,能谱分析等测试手段,分析了某乳品公司碳钢立式蒸发器循环水中的有害成分、腐蚀产物的形貌和元素,测试了循环水中放置669 h和1054 h碳钢试样的腐蚀速率.研究表明:水中含有铁细菌、硫酸盐还原菌、有害的氯离子和硫酸根离子;靠设备一侧腐蚀产物表面发现了菊花状的硫酸盐还原菌;碳钢的腐蚀速率分别为0.6593 mm/a和0.7187 mm/a.综合分析认为,冷却水介质中蒸发器的孔蚀原因是氧的去极化,垢下腐蚀,硫酸盐还原菌和铁细菌腐蚀协同作用的结果.

Analysis of corrosion reason of vertical-type evaporator in the circulated cooling water system

The aim of this work is to analyze the cause of pitting corrosion on mild steel of vertical-type evaporator in one dairy company. Harmful ingredients in circuiting water were obtained using chemical analysis. The morphology and composition of corrosion products were analyzed with SEM, energy spectrum. The corrosion rates of the mild steel samples were calculated from weight loss method in circulating water for 669 h and 1 054 h. The result shows that the circuiting water contains a certain amount of Cl^-, SO4^2- , sulfate-reducing bacteria, iron bacteria, etc. Moreover, conspicuous rosette-shaped microcolonies are found on the inside surface of corrosion products. The corrosion rates of mild steel samples are 0. 6593 mm/a and 0. 7187 mm/a respectively. Finally, we demonstrate that the synergic effect of oxygen depolarization, sulfate-reducing bacteria and iron bacteria, under deposit corrosion is the main cause of pitting corrosion.