Corrosion Behavior of Q235 Steel in Atmospheres Containing SO2 and NaCl

The atmospheric corrosion of metals is a severe problem in marine environments. However, the effects of SO2 and NaCl on the atmospheric corrosion of Q235 steel have not been widely studied. In the present work, electrochemical impedance spectroscopy was conducted to exploit the initial corrosion properties of Q235 in simulated atmospheric environments containing different contents of SO2 and NaCl. The solution resistance (Rs) and polarization resistance (Rp) of electrodes covered with pre-deposited NaCl were continuously monitored. The results showed that both SO2 and NaCl promoted the corrosion rate of Q235 steel. The pre-deposited NaCl maintained the moisture of the metal surface to ensure continued corrosion. The thickness of the electrolyte layer on the metal surface decreased with increasing SO2 content. A thin electrolyte layer could increase the Cl− concentration and reduce the pH value of the layer. The thin electrolyte layer could also promote the mass transfer of oxygen, thereby accelerating the cathodic reduction reaction. However, the NaCl content played a more important role than that of SO2 in the simulated environments.