Details of the performance, production, and application of galvanized steel pipe with a plastic coating on the outside

A galvanized steel pipe with a plastic coating on the inside is a high-quality steel pipe among steel-plastic pipes. It combines the multiple advantages of galvanized layer and plastic coating layer, and has outstanding performance in many fields:

First, the structure and protection principle of galvanized steel pipe with a plastic coating on the outside

The outer layer is a galvanized layer. Through hot-dip galvanizing or electro-galvanizing process, zinc forms a continuous and dense protective film on the outer surface of the steel pipe. The chemical properties of zinc are more active than iron. In a corrosive environment, the zinc layer will be oxidized first as an anode, sacrificing itself to protect the steel pipe matrix, delaying the rusting process of the steel pipe, and greatly improving the outdoor corrosion resistance and service life of the steel pipe.

The inner layer is coated with thermoplastic plastics, such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), etc., and the plastic is tightly attached to the inner wall of the steel pipe by electrostatic spraying, rotational molding, and other processes. The plastic layer can resist corrosion from a variety of chemical substances. In addition to strong oxidizing acids, it can cope with most acid, alkali, and salt solutions, providing a pure, pollution-free channel for the conveying medium and preventing the inner wall of the steel pipe from being corroded.

Second, the performance characteristics of the outer galvanized and inner plastic coated steel pipe

(a) Excellent corrosion resistance: The outer galvanized steel pipe can cope with atmospheric corrosion and rainwater erosion, and the inner plastic coating can withstand the chemical erosion of the conveying medium. Under double protection, whether it is conveying domestic water, rainwater, or slightly corrosive industrial wastewater, the steel pipe can operate stably for a long time, reducing the cost and inconvenience caused by frequent replacement of steel pipes.

(b) Good hygienic performance: When food-grade lining plastic is selected, the steel pipe fully meets the standards for domestic drinking water transportation, can prevent the dissolution of metal ions and the seepage of plastic additives, ensures the clean and safe water quality, and is very reliable for municipal water supply and community direct drinking water systems.

(c) Higher mechanical strength: Based on the steel pipe matrix, the galvanized steel pipe with plastic coating inherits the high strength of steel and can withstand higher pressure. It is suitable for medium and high pressure steel pipe systems, such as the central heating and hot water supply pipelines of buildings. It can withstand the pressure of hot water circulation and is not easy to deform or break.

(d) Installation convenience: Steel pipe sections with smaller diameters can be connected with threads, which is simple and quick to operate; large steel pipes can be connected with grooves and flanges. These mature connection methods facilitate construction personnel to quickly build steel pipe systems, and it is also easier to disassemble and replace pipe sections during subsequent maintenance.

Third, the production process of galvanized steel pipe with plastic coating

(a) Galvanizing process: Hot-dip galvanizing requires the steel pipe to be degreased, pickled, and rusted first, and then immersed in molten zinc liquid. Zinc and iron react to form an alloy layer and a pure zinc layer; electro-galvanizing is to deposit of zinc ions on the surface of the steel pipe under power to form a coating.

(b) Plastic coating: Electrostatic spraying is to adsorb plastic powder on the inner wall of the steel pipe through high-voltage static electricity, and then heat and solidify; rotational molding is to put plastic powder into the steel pipe, rotate and heat it, so that the plastic is evenly distributed and melted.

Fourth, the application field of galvanized steel pipe with plastic coating

(a) Water supply and drainage system: In the municipal water supply network and indoor and outdoor water supply and drainage projects of buildings, galvanized steel pipe with a plastic coating on the outside ensures the water quality, resists soil corrosion and groundwater erosion, and can withstand water supply pressure. It is an ideal steel pipe to replace traditional galvanized steel pipe.

(b) Fire protection engineering: When transporting fire water, its high strength can withstand the high-pressure impact of fire water, and its corrosion resistance ensures that the inside of the steel pipe is still intact when it is idle for a long time, and it can be put into fire fighting at any time.

(c) Chemical transportation: For the transportation of some chemical raw materials and finished products with weak corrosiveness, this steel pipe can not only meet the basic corrosion resistance requirements but also use its mechanical strength to maintain the stability of the steel pipe and reduce the cost of chemical logistics.