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Why is aluminum galvanized corrosion resistant

Update:13 Jul 2018
Summary:

The significance of hot-dip aluminum-zinc is that after […]

The significance of hot-dip aluminum-zinc is that after the surface of the steel wire is covered with a galvanized steel coil layer, the corrosion resistance is greatly improved, material and resources can be saved, and good economic and environmental benefits are exerted.
The protection effect of the galvanized layer on the steel wire is mainly as follows. When the surface of the galvanized steel wire is intact, only zinc corrosion occurs. Since the zinc corrosion product has a good protection effect on zinc, the corrosion rate is very slow, and the service life is 15 to 30 times that of the ungalvanized steel wire.
The most common situation of color coated plate, color steel plate, color coated roll, and color steel coil is that the aluminum-zinc-plated steel wire is stranded in the strand, in use, scratched on the surface, or the surface is partially damaged by other reasons. Exposure to the environment, if the coating is a non-metallic substance, the exposed steel matrix will soon be eroded by the litter. However, the unique sacrificial protective properties of the galvanized steel wire will make the corrosion rate very slow. This is because the zinc in the coating and the iron in the steel wire constitute the galvanic cell in a humid environment. Since the standard electrode potential of zinc is only 1.05V, which is lower than a 0.036V of iron, zinc is oxidized as an anode, and iron Protected as a cathode. The product after zinc corrosion is very dense. The reaction rate is very slow, which means that the overall corrosion resistance is greatly improved. This method of corrosion protection is called sacrificial anode protection.