Oxidation of 1018 carbon steel in borate medium by in situ EC-STM: Surface morphology of the oxidized ferrite and pearlite phases

Microstructures of low carbon steel are ferrite (Fe-α) and pearlite (alternate mixture of Fe-α and Fe3C) and each one has its own oxidation mechanism. These two phases were identified using in situ electrochemical scanning tunneling microscopy (EC-STM). Real time images were obtained during the immersion of 1018 carbon steel probes in 0.642 M H3BO3 and 0.1 M NaOH, pH 7.8. Two different corrosion mechanisms (oxide characteristics) were identified and correlated with the observed surface changes.