Abstract:

A sodium hypochlorite assisted phosphorus-free passivation program of recirculating cooling water was studied. The result showed that the proper amount of residual chlorine could improve passivation process. With the increase on residual chlorine from 0 to 0.5 mg/L, the uniform and compact blue protective film gradually formed on the surface of carbon steel(CS). The occurrence time of red point increased from 5 seconds to 30 seconds. The corrosion rate of passivated carbon steel in cooling water measured by electrochemical method decreased from 0.1 mm/a to 0.005 mm/a. However, the excess residual chlorine could result in corrosion. Compare with traditional phosphorus-based passivation program, the significant advantage of this program is the lower dosage, shorter passivation time, direct switch to normal running phase after passivation, and more convenient on-site operation.

Key words: recirculating cooling water, phosphorus-free passivation, residual chlorine, carbon steel

摘要：

研究了一种次氯酸钠辅助的循环冷却水无磷钝化方案。结果表明，适量的余氯能改善钝化过程。随着余氯从0增加至0.5 mg/L，碳钢表面逐渐形成均匀致密的蓝色保护膜，红点出现时间从5 s增加至30 s，电化学测量的碳钢在冷却水中的实时腐蚀率从0.1 mm/a降低至0.005 mm/a；而过量的余氯会导致腐蚀。对比传统的含磷钝化，其显著优势是药剂投加量低，成膜时间短，钝化后可直接切换至正常运行阶段，现场操作更方便。

关键词: 循环冷却水, 无磷钝化, 余氯, 碳钢

CLC Number: 

• TQ085+.4