Corrosion resistance: The absolute advantage of galvanized steel sheets
Cold-rolled steel plates have extremely poor corrosion resistance. Rust will appear after being exposed to the air for 2 to 3 days, and obvious red rust will form within one month in a humid environment. The rusting mechanism is that iron reacts with oxygen and water vapor in the air to form loose Fe₂O₃ · nH₂O, which cannot prevent the corrosion from continuing.
Galvanized steel sheets achieve anti-corrosion through zinc coating
Sacrificial anode protection: The electrode potential of zinc (-0.76V) is lower than that of iron (-0.44V). When the coating is damaged, zinc corrodes preferentially, protecting the steel substrate.
Physical barrier function: The zinc layer forms a dense oxide film (ZnO, Zn (OH)₂), preventing corrosive media from coming into contact with the substrate. Hot-dip galvanized steel sheets (with a zinc coating of 275g/m²) can resist rust for 8 to 12 years in industrial environments, which is 50 to 100 times longer than that of cold-rolled steel sheets.
