Mainly used for conveying gas and heating.
In gas, greenhouses, heating the kind of iron pipe is also galvanized pipe, galvanized pipe as a water pipe, the pipe produces a lot of rust scale, yellow water out not only pollution sanitary ware, but also mixed with the non-smooth inner wall of the bacteria, corrosion caused by high content of heavy metals in the water, serious harm to human health. 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.
At present, galvanized pipes are rarely used in cold water pipes of new residential areas, and galvanized pipes are used in hot water pipes of some residential areas. Hot-dip galvanized pipe: In order to improve the corrosion resistance of the steel pipe, the general steel pipe is galvanized. Galvanized steel pipe is divided into hot dip galvanized and electric galvanized. The layer of hot dip galvanized is thick, the cost of electric galvanized is low, and the surface is not very smooth. 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.