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The corrosion investigation of the main water supply pipeline for diverting water from the Luan River to Tianjin is a typical case study on corrosion, revealing the long-term impacts of environmental factors and failed protection measures on large-scale infrastructure. The two water supply pipelines of the Luanhe-to-Tianjin project, built in 1983 (with diameters of 2500 mm and 1800 mm respectively), use a petroleum asphalt anti-corrosion coating of \"three oils and two fabrics\". Many years later, due to the deterioration of the geographical conditions along the area, the soil pH dropped to 5.5–6.0 (slightly acidic), the soil resistivity was only 4–10 Ω·m, and the levels of moisture and salt were high, classifying it as a highly corrosive environment. At the same time, urban wastewater leads to increased microbial activity, exacerbating bacterial corrosion; coupled with stray current interference, this accelerates pipe corrosion. Tests revealed that the anti-corrosion layer was severely aged, with the insulation resistance values ranging from 1 to 2 kΩ·m², which is considered poor ； The average wall thickness decreases by 0.5 mm; locally, pits with a diameter of 15 mm and a depth of 7 mm occur, with an annual corrosion rate of 0.4 mm/year ； 80%–90% of the erosion pits are concentrated in the middle and lower sections of the pipeline, where electrochemical corrosion occurs due to the oxygen concentration difference cell effect. It is ultimately recommended to adopt deep-well anode with external current cathodic protection technology; the investment required is only a fraction of that for rebuilding the double track, making it an economical and efficient solution.