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.
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.
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.
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.
