Hot dip process
Workpiece → degreasing → washing → pickling → washing → dip test help plated solvent → drying Preheat galvanized → finishing → hot dip → cooling → rinsing → drying →inspection
Hot-dip galvanizing layer formation process
Hot-dip galvanizing layer formation process is a procedure of the zinc alloy, the surface of the workpiece in the hot dip plated iron – zinc alloy layer is formed, it makes between the iron and the pure zinc layer is formed between the iron in the iron matrix and the outermost pure zinc layer good binding, the process can be simply stated as follows: when the iron workpiece immersed in the molten zinc was first formed on the interface of zinc and an α solid solution of iron (body centered). This is the matrix metal iron is dissolved in the solid state formed by a crystal with a zinc atom, and is a fusion between the two metal atoms, the attractive forces between atoms is relatively small. Accordingly, when the zinc in the solid melt reaches saturation, the two elements of the zinc-iron atom mutual diffusion, diffusion (or called infiltration) a zinc atom in the iron matrix, migrate in the matrix lattice, gradually forming an alloy with iron, and the diffusion zinc to the molten liquid iron and zinc formation intermetallic compounds FeZn13, sinking into the hot-dip galvanizing pot is dross. When the workpiece is removed from the dip zinc liquid formed on the surface of pure zinc layer is hexagonal. The iron content is not greater than 0.003%.
The protective properties of the hot-dip galvanizing layer
Usually electrically galvanized layer thickness 5 ~~ 15μm, while the galvanized layer is generally more than 35μm, or even up to 200μm. Hot-dip galvanizing good covering power, dense coating no organics inclusion. Is well known, zinc atmospheric corrosion mechanism of mechanical protection and electrochemical protection, under the conditions of atmospheric corrosion surface zinc layer of ZnO, Zn (OH) 2 and the protective film of the basic zinc carbonate, and to slow down the corrosion of zinc to a certain extent, this damaged layer protective film (also referred to as white rust) will form a new layer. Serious destruction of the zinc layer, endangering the iron matrix, the zinc on the base body for electrochemical protection, zinc standard potential of-0.76V, the iron standard potential of -0.44 V., zinc and iron to form a micro-battery, zinc as the anode is dissolved, iron protected as a cathode. Apparently better than electric galvanized hot dip galvanized resistance to atmospheric corrosion of the base metal iron.
Post time: Oct-29-2019