There are two types of galvanized square pipes: hot-dip galvanized square tubes and electro-galvanized square tubes. Hot-dip galvanized square tubes include wet method, dry method, lead-zinc method, and redox method. The main difference between the different hot-dip galvanizing methods is to use a method to activate the surface of the pipe body to improve the quality of galvanizing after acid pickling and cleaning of the steel pipe. At present, the dry method and the redox method are mainly used. The characteristics are shown in the table. The surface of the zinc layer of electro-galvanized zinc is very smooth and dense, with a uniform structure; it has good mechanical properties and corrosion resistance; the zinc consumption is 60% to 75% lower than that of hot-dip galvanizing. Electrogalvanizing has certain technical complexity, but this method is required for single-sided coatings, double-sided coatings with different thicknesses on the inner and outer surface coatings, and galvanizing of thin-walled tubes.
Characteristics of galvanized square tube
(1) For galvanized pipe, the pure zinc layer is densely covered on the surface of the steel. It can prevent any corrosion solution from contacting the steel substrate and protect the steel substrate from corrosion. In a general atmosphere, a zinc layer is formed on the surface of a thin layer of dense zinc oxide. It is insoluble in water, so it protects the steel substrate. If other components form insoluble zinc salt in the zinc oxide and atmosphere, then the corrosion protection effect is more ideal.
(2) The iron-zinc alloy layer is dense and has the characteristics of salt spray atmosphere at sea and atmospheric corrosion resistance of industry;
(3) Due to the firm connection of the galvanized pipe, the miscibility of zinc-iron and strong wear resistance;
(4) Because the galvanized pipe has good ductility and is firmly attached to the alloy layer and steel on the substrate, hot-plating can be cold stamped, rolled, stretched, bent and other forms without damaging the coating;
(5) The galvanized steel pipe adopts hot-dip galvanizing, which is equivalent to annealing treatment