Jackfruit (Artocapus heterophyllus Lam.) and teak (Tectona grandis L.) leaves extracts as green corrosion inhibitors

In this study, the inhibition effect of water and methanol extracts (WE and ME) of raw and ripe jackfruit leaves (JL) and raw teak leaves (TL) on the corrosion of mild steel (MS) in 1M HCl was studied. Weight loss measurements and potentiodynamic polarization techniques were used to investigate the behavior of the above inhibitors. The percentage of inhibition efficiency (% IE) increased with the increasing concentration of inhibitors in 1 M HCl medium. Water extract of ripe JL was found to be the most effective inhibitor and % IE was 73 at the concentration of 400 ppm. The effectiveness of other inhibitors towards corrosion in the descending order is WE of TL, ME of ripe JL, WE of raw JL, ME of TL and ME of raw JL. With the increase of the temperature, even the adsorption of the most efficient inhibitor, WE of ripe JL, decreased and the rate of corrosion increased. According to the estimated adsorption equilibrium constant, Kads and standard Gibbs free energy change, ∆G0ads, adsorption of WEs of ripe JL and TL on mild steel surface mainly observed to be by chemisorption. Potentiodynamic polarization scans have revealed the possibility of mixed type corrosion inhibition by WEs of ripe JL and TL. Keywords. Adsorption, Langmuir isotherm, corrosion inhibitor, weight loss measurements