Electrochemical studies on emulsion coated mild steel in ground water

The corrosion resistance of mild steel immersed in groundwater before and after 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.Electrochemical studies reveal that the corrosion inhibition efficiency of mild steel after emulsion coating is found to be greater than 95%.Electrochemical studies lead to the conclusion that the mild steel tank used in water storing may be given a coat of emulsion coating to improve the life time of the mild steel tank.Mild steel pipelines carrying ground water may be given an inner emulsion coating.AFM study reveals that the film coating is at nano scale level.The AFM parameters, namely, RMS (Sq) roughness (nm), average (Sa) roughness (nm), and maximum peak-to-valley height (Sy) (nm) for the coated system are lower than those for uncoated system.That is after coating, the surface of mild steel becomes smoother.Analysis of SEM images confirms that the coated surface is smoother than the uncoated surface.Contact angle measurement study reveals that after emulsion coating, the mild steel surface becomes hydrophobic in nature.It acquires water repelling nature.So, corrosion inhibition efficiency is greater than 95%.The findings will be useful in transport of mild steel pipelines carrying ground water.