Corrosion Inhibition of High Carbon Steel in Phosphoric Acid Solution by Extract of Black Tea

Black tea extract was estimated as high carbon steel corrosion inhibitor in 1 M H3PO4 solution using non-electrochemical technique (Weight loss, FT-IR and SEM analysis). The maximum inhibition efficiency was found to be 93.79 at 4 g/ L. The results indicated that inhibition efficiency increases as inhibitor concentrations increase. Adsorption studies exhibited that inhibitor adsorbed on the metal surface follow Langmuir adsorption isotherm. The Gibbs free energy of adsorption (∆ Gads = -9.74 kJ mol-1) values strongly supported the physicochemical adsorption of inhibitor molecules over the high carbon steel surface. Scanning electron microscopy (SEM) was applied to study the high carbon steel surface in the presence and absence of extract. The adsorption mechanism of inhibitor molecule deposited on the metal surface was investigated by Fourier transform infrared spectroscopy.