Abstract: The corrosion behavior of low-C medium-Mn steel in a simulated marine environment was investigated by drying-wetting cycles test. Scanning electron microscope (SEM) was used to characterize corrosion morphology. Electron probe micro-analyzer (EPMA) was utilized to observe the cross-section morphology and analyzed the distribution of Mn. X-ray diffraction (XRD) was employed to study the phase analysis of corrosion rust. The results showed that corrosion rate rises quickly at the beginning then decreases subsequently and finally tends to be stable. Corrosion products are gradually transformed into a dense and thick corrosion rust from the loose and porous morphology with the extension of the corrosion time. The main corrosion product in the high chloride ion environment is γ-FeOOH. In the meanwhile， there are many manganese oxides and iron-manganese oxides in the corrosion rust which were not found in other steels. Those corrosion phases can promote electrochemical reaction and accelerate the corrosion process.

Key words: low-C medium-Mn steel, drying-wetting cycles, micro-morphology, corrosion rate, corrosion behavior