Surface inhomogeneity study of carbon steel with GO-doped epoxy coatings using integrated SEM-SVET-LEIS methodology

Purpose The purpose of this paper was to study the surface inhomogeneity and its mechanism for carbon steel using GO-doped epoxy coatings by using integrated SEM-SVET-LEIS research methodology. Design/methodology/approach The surface inhomogeneity of GO-doped epoxy coatings was evaluated via scanning electron microscope (SEM), scanning vibration electrode testing (SVET) and localized electrochemical impedance system (LEIS), which can provide micro-region electrochemical information with 3D distribution maps. Findings SEM image illustrated that GO/EP coating rendered a significant portion of the surface remains relatively intact and smooth against corrosion. SVET tests presented interwoven uniform potential distribution and very small peak values of current density 236.8 µA/cm2, in comparison with higher current density of 947.4 µA/cm2 for carbon steel without GO/EP coating. LEIS tests indicated that impedance peak distribution coefficients (IPDC) of coating specimen was 7.2 pcs/mm2, which is smaller than that of carbon steel without coating with IPDC of 16 pcs/mm2. It was due to excellent performance of GO/EP coating, which might generate stable complexes on the surface and selectively intercept of aggressive ions in seawater. Originality/value The doping composition and surface uniformity of the carbon steel with GO coating directly affect the performance in seawater salt spray environment. The inhomogeneity of GO/EP coatings can be well studied using integrated SEM-SVET-LEIS research methodology, which could be explained by micro-region potential distribution and impedance peak distribution coefficients.