Characterization of initial atmospheric corrosion of conventional weathering steels and a mild steel in a tropical atmosphere

The phases and compositions of the corrosion products of a mild steel (A-36) and two weathering steels (A-588 and COR 420) formed after 3 months exposure to the tropical marine atmosphere of Panama were examined using FTIR and Mossbauer spectroscopy. The results show that amorphous or crystallized iron oxyhydroxides goethite alpha-FeOOH and lepidocrocite gamma-FeOOH are early corrosion products. Maghemite gamma-Fe2O3 and magnetite Fe3O4 have also been identified and found to be prominent components for steels exposed to the most aggressive conditions. The formation of akaganeite beta-FeOOH was observed when chlorides were occluded within the rust. FTIR showed the presence of hematite alpha-Fe2O3 in one sample.