CORROSION INHIBITION BY SHOREA ROBUSTA (SAAL) BARK EXTRACT FOR MILD STEEL CORROSION IN 1 M H2SO4 SOLUTION

Abstract

A novel corrosion inhibitor for mild steel (MS) corrosion has been extracted in methanol solvent from Shorea robusta bark. Qualitative chemical tests, VU, and FTIR measurements were carried out to confirm phytochemicals in the extract. The inhibition efficiency of extract has been studied by using weight loss and potentiodynamic polarization methods. The weight loss measurement has been adopted for the study of inhibitor concentration effect as well as variation of inhibition efficiency for time and temperature. Weight loss measurement reveals the maximum efficiency of 71.47% at ½ hours immersion time in 1000 ppm inhibitor concentration at 18 oC. The 1000 ppm inhibitor can work up to a temperature of 55 oC with 50% efficiency. The open-circuit potential (OCP) measurement reveals the extract as a mixed type of inhibitor. From the potentiodynamic polarization measurement results, the inhibition efficiency of the extract for MS was 93.73% and 75% in the 1000 ppm of inhibitor concentration for as-immersed and immersed conditions respectively. The adsorption isotherm and thermodynamic parameters support that the process is spontaneous and endothermic.