Ductile iron pipes, as a commonly used piping material, play a crucial role in hydraulic projects, urban and rural water supply and drainage, heating systems, and other fields. To further enhance their service life and ensure the safe operation of systems, external anti-corrosion work is particularly important. This article briefly explores the characteristics and applications of various external anti-corrosion coatings for ductile iron pipes.

1.Zinc Spraying with External Asphalt Paint Coating
Zinc spraying combined with asphalt paint coating is a widely adopted external surface coating method by domestic ductile iron pipe manufacturers. For K9-grade ductile iron pipes, the sprayed metallic zinc layer should be no less than 130 g/m², with a zinc purity of at least 99.99%. The external metallic zinc coating must comply with the ISO 8179-1 standard. The thickness of the anti-corrosion paint layer should be no less than 70 μm for the final asphalt paint finish, with a minimum local thickness of no less than 50 μm. Zinc spraying with asphalt paint coating has become the mainstream method for external surface anti-corrosion of ductile iron pipes in China.

2.Polyethylene (PE) Sleeve
It offers excellent hygiene performance, resists delamination on both inner and outer surfaces, meets the requirements for direct drinking water, and withstands corrosion from special media such as seawater and urban wastewater. It is primarily used for drinking water and direct drinking water transmission.

3.Polyurethane Coating

In highly corrosive soil environments, polyurethane external coatings are an ideal choice. They effectively resist erosion from harsh conditions such as seawater, saline-alkali soils, and swamps, providing robust protection for pipelines.

Given China's vast territory, the corrosiveness of soil varies significantly across different regions. Based on the soil environment and corrosiveness assessment of the pipeline installation site, Jin Steel Casting can assist users in designing cost-effective and performance-appropriate external anti-corrosion solutions tailored to meet specific usage requirements.