Hot dip galvanized pipe

The molten base metal in the hot-dip galvanized pipe reacts with the ferroalloy layer, which makes the base metal and the coating combine. Firstly, the hot-dip galvanized pipe is pickled to remove the iron oxide on the steel surface. After pickling, the cleaning solution or ammonium chloride or zinc chloride in the water solution tank is mixed and then put into the hot-dip bath. Zinc plating has the advantages of uniform coating, strong adhesion and long service life. The complex physical and chemical reactions between the steel substrate and the molten pool form a close layer of corrosion-resistant zinc iron alloy structure. The alloy layer is mixed with pure zinc layer and steel base. Therefore, it is resistant to corrosion.


The hot-dip galvanizing layer forms matrix zinc alloy between the outermost pure zinc and iron, and the iron surface zinc alloy layer is formed during the hot-dip galvanizing process, which makes the pure zinc layer combine well with iron and iron. The process can be simply described as: when the workpiece is immersed in the molten zinc iron solution, zinc and iron (core) solid solution are formed at the interface first. This is a base metal of iron. It dissolves in solid state to form crystalline zinc atom. The two metal atoms fuse with each other and the gravity atom is relatively small. Therefore, when zinc is in the saturated solid solution, the atoms of zinc and iron diffuse each other, and the diffusion (or infiltration) of zinc atoms in the iron matrix gradually migrates in the lattice of the matrix, thus forming a kind of iron and molten iron in the molten zinc, forming the intermetallic compound fezn13, sinking the galvanizing pot, namely slag and zinc. When the workpiece moves away from the surface of molten zinc, the pure zinc layer leaches to form hexagonal crystal. The iron content is below 0.003%.


When the temperature is too low, the mobility of zinc is poor, the coating thickness is uneven, it is easy to sag, and the visual quality is poor; when the temperature is high, the fluidity of liquid zinc and zinc is good, it is easy to dissolve from the workpiece, reducing the phenomenon of sagging and wrinkling, with strong adhesion, thin coating, good appearance and high production efficiency; but when the temperature is too high, the iron loss of workpiece and zinc pot is serious, resulting in a large number of zinc slag, which affects the quality of zinc coating , zinc consumption is large, even can't be electroplated. At the same temperature, the immersion time is long and the coating thickness is large. Different temperature, the same thickness, high temperature immersion time length.


Hot dip galvanizing process:


Preparation - Pickling - washing - solubilization - hot dip galvanizing - cooling - passive - Cleaning - sorting - rechecking - Packaging - storage