Ficus racemosa leaf extract for inhibiting steel corrosion in a hydrochloric acid medium

Carbon steel coupons are used to characterize inhibition efficiency and surface properties for different Ficus racemosa leaf extract (FRLE) concentrations including 0, 500, 1000, 1500 and 2000 ppm in an aerated 0.1 M hydrochloric acid solution. The results indicate that carbon steel is significantly protected by FRLE and higher performances are reached with an increase in FRLE concentration up to 1500 ppm (93.11 +/- 1.99%). Additionally, the addition of 2000 ppm FRLE reduced inhibition performance (88.86 +/- 2.15%) due to high inhibition concentrations that could impede the formation of a solid protective film. This also demonstrates that the corrosion of steel is probably retarded via the formation of a protective film which is reinforced by FRLE concentration and exposure time due to the continuous adsorption of FRLE inhibitor components at suitable concentrations. The quantum chemical calculations demonstrate a high binding energy between FRLE molecules and carbon steel and a good thermal stability of the adsorbent layer, as well as an electron abundance of the FRLE species. This could result in a much more compact solid protective layer that could hinder electrochemical corrosion when carbon steel is exposed in an aerated 0.1 M hydrochloric acid solution. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.