Hot dip galvanized pipe molten matrix metal and the reaction of the iron alloy layer, so that the substrate and coating combination of both. Hot dip galvanized pipe is first pickled, the steel surface in order to remove iron oxide, after pickling, by mixing the aqueous solution tank for cleaning solution or ammonium chloride or zinc chloride, and then into hot-dip plating bath. Galvanized with coating uniformity, strong adhesion, long life and other advantages. Steel substrate occurs with molten bath complex physical, chemical reactions, the formation of corrosion-resistant zinc-iron alloy structure closely layer. Alloy layer and layer of pure zinc, steel base blend. Therefore it resistant to corrosion.
hot dip galvanizing layer formation matrix between the outermost layer of pure zinc and iron formation - the process of zinc alloy, iron surface formed during hot dipping - zinc alloy layer, which makes the pure zinc layer between the iron and the very good combination, the process can be simply described as: when the workpiece immersed in molten zinc iron solution, first formed zinc and iron (body-centered) solid solution at the interface. This is the base metal of iron dissolved in the solid state to form a crystalline zinc atom, a fusion between the two metal atoms, the atoms of gravity is relatively small. Therefore, when the zinc in the saturated solid solution, zinc, iron interdiffusion of atoms of two elements, the diffusion (or called infiltration) in the iron matrix of zinc atoms in the crystal lattice of the substrate to migrate gradually to form an alloy with iron, and the diffusion the molten iron in molten zinc to form intermetallic compounds FeZn13, sank galvanized pot, that is dross and zinc. When the workpiece is removed from the surface of molten zinc leaching of pure zinc layer, hexagonal crystals. Iron content is not more than 0.003%.
When the temperature is too low, zinc was poor mobility, coating thickness and uneven, prone to sagging, poor visual quality; temperatures are high, good fluidity liquid zinc and zinc from the workpiece and easy solution to reduce the phenomenon of sagging and wrinkled skin happen, strong adhesion, coating thin, good appearance, high production efficiency; But the temperature is too high, the workpiece and zinc pot iron loss seriously, producing a large zinc slag, affecting dip zinc coating quality, large consumption of zinc, not even plating. At the same temperature, dip time is long, the coating thickness. Different temperatures, requiring the same thickness, the length of time required for the high temperature dip.
Hot dip galvanizing process:
Preparation - pickling - washing - solubilization - hot-dip zinc - Cooling - passive - cleaning - sorting - recheck - packaging - storage