Corrosion inhibition of mild steel in sodium chloride solution by some zinc complexes

► EIS examination of mild steel/NaCl solution containing some zinc complexes. ► Surface microscopy of the mild steel samples by SEM. ► Surface analysis of the mild steel samples by XRD and EDX. ► pH-metry of the test solutions after contact with mild steel samples. ► Correlation between corrosion inhibition, pH-metry and surface analysis results. The corrosion inhibitive effect of zinc acetate, zinc acetylacetonate and zinc gluconate on the mild steel immersed in 3.5% NaCl solution was evaluated by electrochemical impedance spectroscopy (EIS). The results revealed superiority of zinc gluconate whilst zinc acetate showed inferior corrosion inhibition. The surface of the samples exposed to the inhibited solutions was analyzed using XRD and SEM techniques. The pH measurement of the test solutions before and after corrosion, also before and after addition of Fe +2 and Fe +3 revealed that the superior inhibition of zinc gluconate is related to formation of insoluble corrosion products on the mild steel surface.