High Temperature Corrosion of S31035 for 630° Coal-fired Power Plant Boiler

The work aims to study high temperature sulfur corrosion resistance of S31035, which is used as the key candidate tube of high-temperature heating surface of 630 boiler. Corrosion tests were conducted by placing S31035 steel coated by high or low alkali coal ash in simulated flue gas (700, SO2 volume concentration of 0.3%). The samples were weighted at intervals during the test, then corrosion kinetics curve was plotted. The macro characteristics of the samples were observed, and the surface/cross-section morphology and composition of the corrosion products were analyzed by X-ray diffraction equipment, electron microscope and energy dispersive spectrometer. The results showed that the S31035 steel undergone corrosion after coated by low alkali coal ash, with relatively dense (FeCr)2O3 oxide film on the surface of the sample. Meanwhile corrosion product film was very thin. However, the corrosion products grew in layer and peeled off severely in the high alkali coal ash, weight loss exceeded 27 mg/cm2 after 2 000 h. Cr and S were enriched in the corrosion layer, resulting in serious high temperature sulfur corrosion. It showed that the alkali metal content of coal ash was the key factor affecting the high temperature sulfur corrosion resistance of S31035. In the same high sulfur environment, the high temperature sulfur corrosion resistance for low alkali coal ash was good, but for high alkali coal ash was poor. S31035 can be applied to the high temperature heat exchange components of 630 coal-fired boiler. When burning high sulfur coal with high alkali coal ash, the high temperature corrosion can be inhibited by strengthening the removal of coal ash on the surface of heating surface.