某电厂低温省煤器ND钢发生大面积腐蚀,采用宏观观察、化学成分分析、金相检验、硬度测试、扫描电镜分析、X射线衍射分析、离子色谱分析等方法研究腐蚀原因。结果表明:试样的化学成分、显微组织、显微硬度等均符合标准要求;泄漏的水溶解了烟气中的硫化物,形成酸性溶液并吸附到管子外表面,溶解的F^-、Cl^-和SO^2-₄破坏了ND钢管壁表面的保护膜,导致低温省煤器发生大面积腐蚀。最后提出了改进建议,以避免低温省煤器ND钢发生大范围腐蚀。

A large area of corrosion occurred in ND steel of low temperature economizer in a power plant. The causes of corrosion were studied by means of macroscopic observation, chemical composition analysis, metallographic examination, hardness test, scanning electron microscope analysis, X-ray diffraction analysis and ion chromatography analysis. The results show that the chemical composition, microstructure and microhardness of the samples all met the requirements of the standard. The leaked water dissolved the sulfide in the flue gas to form an acidic solution, which was adsorbed to the outer surface of the pipe. The dissolved F^-, Cl^-and SO^2-₄ destroyed the protective film on the surface of the ND steel pipe wall, resulting in large-scale corrosion of the low-temperature economizer. Finally, suggestions for improvement were put forward to avoid large-scale corrosion of ND steel in low-temperature economizer.