What is aluminizing
Sep. 22, 2020
What is aluminizing
Aluminizing, according to the structure of the aluminized layer, can be divided into hot-dip aluminizing and diffusion aluminizing. Hot-dip aluminizing is hot-dip aluminizing, which is mainly used for anti-corrosion protection when the material is in service at 600℃. Diffusion aluminizing is mainly used to improve the corrosion protection of materials under high temperature conditions.
Hot-dip aluminized steel parts with clean surface are immersed in molten aluminum or aluminum alloy melt at 680℃-780℃ to obtain hot-dip aluminized layer. The steps are: degreasing → descaling → pretreatment → hot-dip aluminum plating.
The formation of hot-dip aluminum coating can have the following three steps:
1) The clean steel parts are immersed in molten aluminum, and the surface of the steel parts is wetted by the molten aluminum.
2) A diffusion layer composed of aluminum-iron intermetallic compound is formed on the surface of the steel, and the diffusion layer is composed of FeAl3 (θ phase) and Fe2Al5 (η phase).
3) When the workpiece is lifted from the molten aluminum, a coating layer with the same composition as the molten aluminum is attached to the surface.
The hot-dip aluminized layer is formed by the diffusion layer and the plating layer, and has atmospheric corrosion resistance and heat resistance.
