Hot-dip galvanized steel pipes are widely used in construction, machinery, coal, chemical, electric power, railway vehicles, automobile industry, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, mining machinery and other manufacturing industries.
Galvanized steel pipes are welded with hot-dip or galvanized steel. Zinc plating can increase the corrosion resistance of steel pipes and prolong their service life. Galvanized pipes are widely used, in addition to pipelines for general low-pressure fluids such as water, gas, oil, etc., and also used as oil well pipes and oil pipes in the petroleum industry, especially in offshore oil fields, and oil heaters and condensation of chemical coking equipment. Cooler, coal distillate oil exchanger pipe, and trestle pipe pile, support pipe for mine tunnel, etc.
The hot-dip galvanized tube is obtained by reacting a molten metal with an iron matrix to produce an alloy layer, thereby combining the substrate and the plating layer. Hot-dip galvanizing is to pickle the steel pipe first, in order to remove the iron oxide on the surface of the steel pipe, after pickling, it is washed by ammonium chloride or zinc chloride aqueous solution or a mixed aqueous solution of ammonium chloride and zinc chloride, and then fed. Hot dip plating tank. Hot-dip galvanizing has the advantages of uniform plating, strong adhesion and long service life.
The galvanized pipe and the molten plating solution undergo complex physical and chemical reactions to form a corrosion-resistant structure of a zinc-iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe base, so it has strong corrosion resistance.
The cold-galvanized pipe is electro-galvanized, with a small amount of galvanizing, only 10-50g/m2, and its corrosion resistance is much worse than that of hot-dip galvanized pipe. Regular galvanized pipe manufacturers, in order to ensure quality, most do not use electro-galvanizing (cold plating). Only small companies with small equipment and old equipment use electro-galvanized steel, of course, their prices are relatively cheaper. The Ministry of Construction has officially laid down the cold-galvanized pipe with backward technology and the use of cold-galvanized pipe as water and gas pipe.
The galvanized layer of the cold-galvanized steel pipe is an electroplated layer, and the zinc layer and the steel pipe base are separately layered. The zinc layer is thin, and the zinc layer is simply attached to the steel pipe base and is easy to fall off. Therefore, its corrosion resistance is poor. In new homes, the use of cold-galvanized steel pipes as water supply pipes is prohibited.