The Transformation of Corrosion Products on Weathering Steel by Visible-Light Illumination under Simulated Marine Atmospheric Condition

This study has explored the visible-light illumination promoted corrosion behavior of weathering steel in simulated marine atmospheric condition. Open circuit potential measurements supplied a direct insight on this photovoltaic effect. To obtain better understanding on this process, the corresponding surface electronic properties together with its microstructures and chemical composition variations were characterized by Mott-Schottky analysis, AFM, XPS and confocal Raman microspectroscopy. All these combined results revealed that the rusted weathering steel sample collected in the dark displayed n-type photo-response due to the presence of hematite (α-Fe 2 O 3 ), maghemite (γ-Fe 2 O 3 ), lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) on its surface. Whereas under illumination, the photogenerated electron-hole pair not only facilitated anodic dissolution and chloride ion adsorption but also leading to hematite to magnetite (Fe 3 O 4 ) transformation in the metal/corrosion layer interface.