Galvanized externally and plastic-coated internally steel pipe is a new type of corrosion-resistant pipe, manufactured through a composite process of "hot-dip galvanizing the external surface and coating the internal surface with plastic." It cleverly combines the outdoor corrosion resistance of the galvanized layer with the anti-fouling and wear-resistant properties of the plastic coating, effectively addressing the pain points of traditional steel pipes, which are prone to external rust and internal scaling, making it a mainstream choice for applications such as municipal water supply, building water supply and drainage, and fire protection piping.

The core production process consists of two steps: The external surface is hot-dip galvanized, where the steel pipe is immersed in molten zinc to form a uniformly thick zinc alloy layer. This effectively resists oxidative corrosion from soil, rainwater, and the atmosphere, preventing rust on the external surface of the steel pipe during outdoor or buried use. The internal surface is coated with a food-grade plastic coating such as epoxy resin or polyethylene using electrostatic spraying or hot-melt adsorption technology. After curing, the coating forms a smooth, dense protective film, isolating the steel from direct contact with water, preventing rust and contamination of the internal wall, while also reducing water flow resistance and energy consumption. Compared to single-use corrosion-resistant pipes, it offers three core advantages: First, it offers corrosion resistance and durability. The galvanized coating extends the lifespan of the outer wall by 3-5 times that of ordinary steel pipe, making it suitable for complex environments such as underground and outdoor installations. Second, it offers internal pollution protection and cleanliness. The food-grade plastic coating meets drinking water hygiene standards, resists rust and scaling, and ensures safe water quality, making it particularly suitable for domestic drinking water transportation. Third, it balances strength and lightness. The base steel pipe retains its high strength and can withstand high water pressure, while the internal and external coatings do not significantly increase weight, making it easy to transport and install.

In practical applications, it is the preferred solution for residential water supply pipes, protecting against underground soil corrosion while ensuring clean water for residents. It is also a reliable solution for fire protection pipes, with its galvanized outer wall resisting aging and its plastic-coated inner wall resisting clogging, ensuring smooth emergency water supply. It is also a practical choice for agricultural irrigation pipes, resistant to soil salinity and alkali corrosion, and its smooth inner wall reduces irrigation energy consumption. It will play a vital role in a wide range of consumer and industrial sectors in the future.