Cause Analysis and Treatment of Internal Corrosion and Leakage of Boiler Water Wall Tubes

The causes of severe corrosion of internal corrosion and leakage of the water wall tubes in a boiler were analyzed. Corrosion products on the inner surface of water wall tubes were studied by chemical element analysis, metallographic examination, SEM, EDS and XRD, the results showed that the main reason was the condenser copper tube corrosion, leading to the condensation abnormality. Cu2+ deposited on the inner wall of the water wall surface had a damaging effect on the tube protective film. As the runtime went on, pitting corrosion occurred. Phosphate promoted the deposition of metallic elements such as Cu on the tube inner surface and accelerated the corrosion. Corrosion products generated continuously and attached on the inner wall, made the tube thinning and affected the heat transfer effect. The tube was in a state of overheat in the runtime, the microstructure gradually aged. The tube wall thinning and material aging together leaded to the leakage of the tubes due to the action of the internal medium pressure. To prevent similar accident, some concrete treatment measures were suggested.