Ductile iron water supply pipes have the advantages of high strength, toughness, good vibration resistance, corrosion resistance, and easy installation. Its strength is higher than steel pipes, its elongation is greater than 10%, and its corrosion resistance is stronger than steel pipes. Ductile iron pipes are used as water distribution pipes to ensure water quality. When the ductile iron pipe leaves the factory, the outer surface is generally sprayed with a zinc layer or coated with asphalt. The anti-corrosion inside the pipe is coated with cement mortar lining. Therefore, the ductile iron pipe shipped from the factory already has a certain degree of anti-corrosion, and there is no need to add special anti-corrosion measures. The anti-corrosion performance of the selected ductile iron pipe should meet the anti-corrosion standards.

The main chemical components of ductile iron pipe are carbon, silicon, manganese, phosphorus, sulfur and magnesium, which are determined by their own material composition, and their resistance is large, so it is not easy to produce electric corrosion; After graphite becomes spherical, the compactness of the material is improved,and effectively prevents the invasion of external oxidizing gas, and further improves the corrosion resistance of ductile iron pipes，and the external corrosion protection of nodular cast iron pipe adopts zinc coating and bituminous coating,thus it can effectively prevent the electrochemical corrosion.In contact with soil, the metal zinc will gradually transform into a compact, cohesive and continuous zinc salt layer. The outer layer of bituminous paint (sealing pores) will transform zinc into insoluble zinc salts rather than soluble zinc hydroxide.