Welded steel pipe with hot dip coating or electro-galvanized coating on the surface of galvanized steel pipe. Galvanizing can improve the corrosion resistance of steel pipes and prolong their service life. Galvanized pipe is an alloy layer produced by the reaction between molten metal and iron matrix, which combines the matrix with the coating. Hot dip galvanizing is to pickle the steel pipe first. In order to remove iron oxide from the surface of steel pipe, it is washed in the tank of ammonium chloride or zinc chloride aqueous solution or mixed aqueous solution of ammonium chloride and zinc chloride after pickling, and then sent to the hot dip plating tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The matrix of hot-dip galvanized steel pipe, galvanized pipe and molten plating solution have complex physical and chemical reactions, forming a dense corrosion-resistant zinc-iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix. Therefore, it has strong corrosion resistance.
Iron is more active chemically and reacts more easily in air, so galvanized steel pipes will be better.