Galvanized Steel Pipes
Hot-dip galvanized steel pipes are widely used in construction, machinery, coal mining, chemical industry, electric power, railway vehicles, automobile industry, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, prospecting machinery and other manufacturing industries.
Galvanized steel pipe: welded steel pipe with a hot dip or electro galvanized surface. Galvanization can increase the corrosion resistance of steel pipes and prolong the service life. Galvanized steel pipe has a wide range of uses, in addition to being used as a pipeline for general low pressure fluids such as water, gas and oil, it is also used as an oil well pipe and oil pipeline in the petroleum industry, especially in the marine oil fields, as an oil heater, condensation cooler and coal distillation and oil washing exchanger for chemical coking equipment, and as a support frame pipe for trestle pipe piles and mining pits, etc.
Hot-dip galvanized pipe is made by reacting the molten metal with the iron substrate to produce an alloy layer, thus combining both the substrate and the coating. Hot-dip galvanizing is to pickle the steel pipe first, in order to remove the iron oxide on the surface of the pipe, after pickling, it is cleaned by ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution bath, and then sent to the hot dip galvanizing bath. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The hot-dip galvanized steel pipe substrate reacts with the molten plating solution in a complex physical and chemical reaction to form a corrosion-resistant, structurally compact zinc-iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe substrate, so its corrosion resistance is strong.
Cold galvanized pipe is galvanized, and the amount of galvanization is very little, only 10-50g/m2, and its own corrosion resistance is much worse than that of hot galvanized pipe. Most of the regular galvanized pipe manufacturers do not use electro galvanizing (cold galvanizing) in order to ensure quality. Only those small enterprises with small scale and obsolete equipment use electro galvanizing, and of course their prices are relatively cheaper. The Ministry of Construction has formally issued the following order to eliminate the backward technology of cold galvanized pipes and forbid the use of cold galvanized pipes for water and gas pipes. Cold galvanized steel pipe galvanized layer is an electroplated layer, the zinc layer and the steel pipe substrate independent of each other. The zinc layer is thin, and the zinc layer is simply attached to the steel pipe matrix and easily peels off. Therefore, its corrosion resistance is poor. In new residential buildings, it is prohibited to use cold galvanized steel pipes as water supply pipes.
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