In-Situ Electrochemical Monitoring and Ex-Situ Chemical Analysis of Epoxy Coated Steels in Sodium Chloride Environment Using Various Spectroscopic Techniques

The effect of immersion time and chloride ion concentration on the early stage of corrosion behavior of scratched epoxy-coated carbon (SM) and chromium containing low-alloy steel (H5) samples were investigated in an in situ manner using localized electrochemical impedance spectroscopy. The results revealed that, the H5 samples had significantly higher impedance values than the SM, which indicated higher corrosion resistance of H5 samples. The drop in impedance magnitude was observed for higher Cl- ion concentration, which indicated that breakdown of passive film had been initiated by Cl- ion resulting in localized corrosion attack of the surface. The morphological and elemental studies showed the formation of green rust and a very stable hydroxide (CrxFe1-x(OH)(2)) on SM and H5 surface respectively as a corrosion product. Hence, the H5 could be a hopeful material with extremely high corrosion resistance for the use as steel structures.