The galvanized steel coils manufacturers china said that the hot-dip galvanized coil is a thin steel coil that is immersed in a molten zinc tank and adhered to a thin layer of zinc on its surface. The main process currently used is continuous galvanizing. The steel coil is immersed in a zinc-plated plating tank to form a galvanized steel coil.
Electroplating zinc is based on the principle of electrochemistry. The zinc ingot is used as the anode. After the zinc atom loses electrons, it becomes an ionic state and dissolves into the electrolyte. The steel strip acts as a cathode, and the zinc ions are electronically reduced on the steel strip to form zinc atoms accumulating at the cathode. The surface layer forms a plating layer.
1. Different thickness of galvanized coil and galvanized coil galvanized layer
The amount of galvanizing of hot-dip galvanizing is unlikely to be too small, usually 50-60 g/m2 for the smallest double sided and 600 g/m2 for the maximum. The galvanized layer of the electro-galvanized coil can be very thin, with a minimum of 15 g/m2 and a maximum of about 100 g/m2. In addition, electro galvanized can be plated on only one side or galvanized on both sides, and hot-dip galvanizing must be galvanized on both sides.
2. Hot-dip galvanized coils and electro-galvanized coils are fundamentally different in the microstructure of the coating.
There is a layer of slightly brittle compound between the hot-dip galvanized pure zinc coating and the steel strip substrate. When the pure zinc coating is crystallized, most of the zinc is formed, and the coating is uniform and non-porous. The zinc atom of the electroplated zinc layer is deposited on the surface of the steel strip only, and it is physically attached to the surface of the steel strip. There are many holes to dry, which is easy to cause pitting due to the corrosive medium, so the hot-dip galvanized coil is more resistant than the electro-galvanized coil. corrosion.
3. Different heat treatment processes for hot-dip galvanizing and electro-galvanized coils
Hot-dip galvanized coils are generally made of chilled coils, which are continuously annealed and hot-dip galvanized on a galvanizing line. The steel strip is cooled again after a short period of time, and the strength and plasticity are affected. The electro-galvanized coil is made from CRC, which basically guarantees the same processing performance of the CRC, but its complicated process also increases the production cost.
4. Hot-dip galvanized coil has the characteristics of thick zinc layer, good corrosion resistance, and low production cost compared with electro-galvanized steel coil.
In the hot-dip galvanizing process, when the steel coil passes through the zinc pot, the zinc liquid is attached to the surface of the steel coil, and the air knife blows off the excess zinc liquid, so it is easy to produce a thick-plated steel coil. In recent years, in order to reduce production costs and meet environmental protection requirements, domestic auto and home appliance companies have gradually replaced hot-dip galvanized coils with electro-galvanized steel coils.