Hot-dip galvanized pipe

Hot dip galvanized pipe is made of molten metal and iron matrix reaction to produce alloy layer, so that the matrix and the coating of the two combination. Hot dip galvanizing is to first pickling the steel pipe. 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 mixed aqueous solution of ammonium chloride and zinc chloride, and then sent into the hot dip plating tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. Complex physical and chemical reactions occur between the steel tube substrate and the molten bath to form a compact zinc-iron alloy layer with corrosion resistance. The alloy layer is integrated with the pure zinc layer and the steel tube matrix. Therefore, its corrosion resistance is strong.

1. Uniformity of galvanized layer: steel tube sample shall not turn red (copper plating color) after 5 consecutive impregnations in copper sulfate solution.

2, surface quality: the surface of galvanized steel pipe should be complete galvanized layer, there should be no black spots and bubbles on the plating, allowing a small rough surface and local zinc tumor.

3, galvanized layer weight: according to the requirements of the customer, galvanized steel pipe can be measured zinc layer weight, its average should not be less than 500g/ square meter, including any sample should not be less than 480g/ square meter.

Cold galvanized pipe

Cold galvanized is electric galvanized, galvanized amount is very small, only 10-50g/m2, its own corrosion resistance is much different than hot galvanized pipe. Regular galvanized pipe manufacturers, in order to ensure quality, most do not use galvanizing (cold plating). Only small businesses with obsolete equipment use galvanizing, and of course their prices are relatively cheap. The Ministry of Construction has officially announced the elimination of cold galvanized pipes with backward technology, and it is not allowed to use cold galvanized pipes as water and gas pipes in the future. The zinc layer is an electric coating, and the zinc layer is layered independently with the steel tube substrate. Zinc layer is thin, zinc layer is simply attached to the steel tube matrix, easy to fall off. So its corrosion resistance is poor. It is prohibited to use cold galvanized steel pipes as water supply pipes in newly built houses.

use

The iron pipe used in gas, greenhouse and heating is also galvanized pipe. Galvanized pipe, as a water pipe, produces a large amount of rust and scale in the pipe. The yellow water flowing out not only pollues sanitary ware, but also contains bacteria bred on the unclean inner wall. In the 1960s and 1970s, developed countries began to develop new types of pipes, and have banned galvanized pipes. China’s Ministry of Construction and other four ministries and commissions also issued a document to prohibit galvanized pipes from 2000. Galvanized pipes are rarely used in cold water pipes of new residential areas, and some residential hot water pipes use galvanized pipes.

Production procedure

Galvanized steel pipe has the following production steps:

Black inspection. Hanging material → Skim → Rinsing → pickling Clean. Dipping aid → Hot air drying. Hot dip galvanizing → Cooling. Passivation and rinsing. unloading Inspection and repair → Packing for storage and transportation.