Solanum nigrum as natural source of corrosion inhibitor for mild steel in sulphuric acid medium

The corrosion inhibition potential of mild steel in 1M H2SO4 by Solanum nigrum extract was studied using weight loss method, potentiodynamic polarisation method, ac impedance studies and SEM technique. Weight loss measurements, carried out at three different temperatures, 303, 313 and 323 K, revealed the increase in inhibition efficiency with increasing concentration of the plant extract as well as the temperature of the system. Thus, the inhibitor exhibited the chemisorption mechanism following Temkin adsorption isotherm. Free energy of activation Delta G was also calculated so as to confirm the chemisorption process. Results of polarisation study revealed the mixed mode of inhibition. SEM studies supported the adsorption of inhibitor over the metal surface. The anticorrosion effect of S. nigrum is attributed to the presence of solasodine which was isolated and studied by theoretical, electrochemical and IR techniques. The possible adsorption mechanism of the inhibition is discussed vis-a-vis the presence of hetero atoms of solasodine.