Abstract
Corrosion behavior of galvannealed steel was studied under various corrosive circumstances and was compared with that of galvanized or electrogalvanized steel.
The results obtained were as follows:
1) The corrosion rate of galvannealed steel was lower than those of other zinc plated steels.
2) The coating layer of the galvannealed steel was composed of Fe-Zn alloy (mainly of δ1-phase) and its natural electrode potential was nobler than those of other zinc plated steels.
3) Zinc of the coating layer was preferentially dissolved by corrosion so that iron was enriched on the coating surface to be converted into red rust, which prevented the internal zinc from dissolution. However, it took a longer time for the substrate metal of galvannealed steel than other zinc plated steels to be corroded into the red rust. Therefore, it was concluded that the coating layer of galvannealed steel has very high corrosion resistance.
