Galvanostatic optimization of polyaniline coating on mild steel in tartrate medium for corrosion protection

Abstract

Optimization of polyaniline (PANI) coating on mild steel (MS) surface has been studied in 0.3 M aniline + 0.2 M sodium potassium tartrate (Na-K Tartrate) by galvanostatic polarization. The current densities of  0.5, 0.75. 1 and 2 mA cm^-2 are used for the electrodeposition of PANI on MS. The obtained PANI coatings have been characterized for its morphology using an optical microscope and corrosion performance by using potentiodynamic polarization in 0.4 M Na₂SO₃ solution simulating an industrial environment. The results reveal a sequential process of dissolution of MS, passivation of MS by forming tartrate salt followed by oxidation of aniline monomer and subsequential nucleation and growth of PANI coating. It is found that the PANI coating obtained at 0.5 mA cm^-2 results in better coating producing corrosion inhibition efficiency (IE) of approximately 90% compared to IE of about 75% for coating obtained at 2 mA cm^-2.