Electrochemical studies on the corrosion resistance of mild steel in 1 M HCl solution before and after emulsion coating

The corrosion resistance of mild steel immersed in 1 M HCl before and after coating of Durable exterior emulsion coating (Emulsion coating) has been evaluated by electrochemical studies such as polarization study and AC impedance spectroscopy. When a protective film (emulsion coating) is formed on metal surface, corrosion resistance of the metal increases and hence LPR value increases and corrosion current decreases. Similarly, when a protective film is formed on the metal surface, corrosion resistance increases, Rt values, impedance values and phase angle increase whereas Cdl values decrease. The study reveals that, after emulsion coating the corrosion resistance of mild steel in 1 M HCl increases because, the LPR value increases and corrosion current decreases as revealed by polarization study. It is also inferred from AC impedance spectra that when mild steel coated with emulsion coating is immersed in 1 M HCl the corrosion resistance of mild steel is increased. This is due to the fact that the emulsion coating on the mild steel is stable in the presence of 1 M HCl. The corrosion inhibition efficiency calculated from the charge transfer resistance values is found to be 99.99%. After emulsion coating corrosion resistance of mild steel increases, Rt values, impedance values and phase angle increase whereas Cdl values decrease. Electrochemical studies lead to the conclusion the mild steel tank used in pickling industry to store concentrated hydrochloric acid may be given a coat of emulsion coating to improve the life time of the mild steel tank in the pickling industry.