Corrosion and Leakage Causes of Carbon Steel Pipe in Open Circulating Cooling Water System

The corrosion and leakage occurred in a carbon steel pipe of open circulating cooling water system in a thermal power plant. The corrosion reasons were analyzed by means of macroscopic inspection, metallographic detection, scanning electron microscopy and energy spectrum. The results showed that the circulating water contained a large number of chloride ions and sulfate ions. The currently used scale and corrosion inhibitors had poor corrosion inhibition performance on carbon steel materials, which led to serious electrochemical corrosion on the inner wall of carbon steel pipe. The corrosion process was accelerated because the concentration ratio of circulating water was over high and the pH value was low for a long time. It was suggested that the corrosion inhibition effect on carbon steel should be mainly investigated in the selection test of scaling corrosion inhibitor, and the quality supervision of circulating water should be strengthened to ensure the safe and stable operation of circulating water system.