Fabrication and optical emission spectroscopy of enhanced corrosion-resistant CPEO films on Q235 low carbon steel

Abstract The oxide films on Q235 low carbon steel as a cathode were quickly prepared by cathodic plasma electrolytic oxidation (CPEO) in 80 vol% glycerol electrolyte within 9 min. The morphology, composition and microhardness of oxide films were analyzed. The corrosion behaviors of bare steel and CPEO films were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The optical emission spectroscopy (OES) was collected and the electron temperature in plasma discharge envelope was calculated. It was found that the CPEO oxide films contained FeO phase, Fe 2 O 3 phase and some dispersed carbon particles. The plasma discharge envelope contained many active carbon, iron and oxygen species. The electron temperature in the plasma discharge region was over 5000 K and meanwhile the surface temperature of steel is over 1000 °C. The CPEO oxide film on Q235 steel grew linearly with 10.89 μm/min. The CPEO treated Q235 low carbon steel had a good corrosion resistance with lower corrosion current density and higher impedance.