Corrosion inhibition of aluminum under basic conditions using Medicago sativa L. extract - thermodynamic studies

摘要

In this research, corrosion inhibitors were synthesized using locally available biomass, alfalfa plant. The inhibitor performance was evaluated at different operating conditions and the effect of process variables, namely inhibitor concentration (1-5%v/v), operating temperature (308.15-328.15 K) and method of extraction (alcohol and aqueous) were studied. The corrosion rate of aluminum decreased with increase in inhibitor concentration and the best result attained was 3.7 mg cm(-2) h(-1) with 5%v/v AALE and 308.15 K. The increase in temperature resulted in the decrease in inhibition efficiency, which could be related to detachment of inhibitors at elevated temperatures. The Langmuir adsorption Isotherm fitted well to the corrosion experiment data (R-20.990) and thermodynamic parameters were calculated. The value of separation factor (0L1) confirmed the favorable adsorption of corrosion inhibitor on the metal surface. Surface characterization of the green inhibitor using scanning electron microscopy was conducted to understand the morphology and FTIR spectrum was used to identify the main functional groups for Alfalfa extracts. The alcoholic extract possessed comparatively higher number of surface-active groups and produced better performance than aqueous extract. Arrhenius plots were employed to determine the activation energy. Tafel plot was used to determine theoretical corrosion current and potential. Electrochemical impedance spectroscopy inhibition efficiency was found to be 90.91% with 5% AALE.