Severely external corrosion has occurred on the ductile iron pipelines tube, which caused leakage and affected the drinking water supply of numerous people. The tube was made up of QT400 ductile iron with external and internal protective coatings. The service environment was the underground of a riverbed close to residential areas. In this study, this failure and its mechanism were studied through field investigations and laboratory experiments. The penetration rate of the localized corrosion is twice higher than that of uniform corrosion. It is perceived that DC stray current causes the localized corrosion, which results in smooth and black-deposits-covered morphology. Microorganisms, especially sulfate-reducing bacteria (SRB) in the soil plays an auxiliary role in the failure process. Additionally, the micro-galvanic corrosion between graphite and matrix promotes the failure. This study shows that an in-depth investigation on the stray-current corrosion in buried cast iron pipes is critical, although sacrificial anodes have been adopted.

球墨铸铁管道管道发生严重外腐蚀，造成渗漏，影响了众多群众的饮水供应。该管由带有内外保护涂层的 QT400 球墨铸铁制成。服务环境为靠近居民区的河床地下。本研究通过现场调查和实验室实验对这种失效及其机理进行了研究。局部腐蚀的渗透速度是均匀腐蚀的两倍。据认为，直流杂散电流会导致局部腐蚀，从而导致光滑和黑色沉积物覆盖的形态。土壤中的微生物，尤其是硫酸盐还原菌（SRB）在破坏过程中起着辅助作用。此外，石墨与基体之间的微电腐蚀促进了失效。这项研究表明，尽管采用了牺牲阳极，但对埋地铸铁管道中杂散电流腐蚀的深入研究至关重要。