Definition And Classification Of Galvanized Steel Pipe

Galvanized steel construction pipe is a welded steel pipe with a hot-dip or electro-galvanized surface. Galvanizing can increase the corrosion resistance of the steel pipe and prolong its service life.

The galvanized pipe is widely used, not only as the pipeline for water delivery, gas, oil and other general low-pressure fluid, but also as the oil well pipe and oil pipe of the petroleum industry, especially the offshore oil field, the oil heater, condensate cooler, coal distillate wash oil exchanger pipe of the chemical cooking equipment, as well as the trestle pipe pile, the support frame pipe of the mine tunnel, etc.

Classification of galvanized steel pipes:

Galvanized steel pipe is divided into cold galvanized steel pipe and hot galvanized steel pipe. Cold galvanized steel pipe has been banned, the latter is also advocated by the state can be used temporarily.Hot dip galvanized steel pipe is widely used in fire protection, electric power, and highway.

Hot-dip galvanized pipe:

Hot-dip galvanized pipe is to make molten metal react with iron matrix to produce an alloy layer, so that the matrix and coating are combined.

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 cleaned by ammonium chloride or zinc chloride aqueous solution or the mixture of ammonium chloride and zinc chloride aqueous solution tank, and then it is sent into the hot-dip galvanizing tank.

Hot-dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life. The complex physical and chemical reactions between the hot-dip galvanized steel pipe matrix and the molten bath form a zinc-iron alloy layer with a close corrosion-resistant structure. The alloy layer is integrated with a pure zinc layer and steel pipe matrix, so it has strong corrosion resistance.

Cold galvanized pipe:

The cold galvanizing pipe is galvanizing, the amount of galvanizing is very little, only 10-50g / m2, its corrosion resistance is much different from that of hot galvanizing pipe. Regular galvanized pipe manufacturers, in order to ensure the quality, most do not use galvanizing (cold plating). Only those small-scale and old equipment small enterprises use galvanizing, of course, their prices are relatively cheap.

The Ministry of construction has officially eliminated the technologically backward cold galvanized pipes, which are not allowed to be used as water and gas pipes. The galvanized layer of cold galvanized steel pipe is an electroplated layer, and the zinc layer is separated from the steel pipe substrate. The zinc layer is thin and easy to fall off. So its corrosion resistance is poor. In newly built houses, it is forbidden to use cold galvanized steel pipes as water supply pipes.