Analysis of Garcinia indica Choisy extract as eco-friendly corrosion inhibitor for aluminum in phosphoric acid using the design of experiment

The inhibiting performance of Garcinia indica Choisy extract was studied on Al in phosphoric acid solution via electrochemical impedance spectroscopy technique and by using response surface methodology (RSM) of the design of experiment. The surface analysis was carried out using scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX) to affirm the adsorption of inhibitor on the surface of metal. In the study, the influence of three process variables (extract concentration, acid concentration, and temperature) are considered on the inhibition efficiency of Al in acid. The process variables considered for the study were taken in 3 levels: temperature (X1) at 30 ^◦C, 40 ^◦C, and 50 ^◦C, extract concentration (X2) at 0.1, 0.3 and 0.5 gL^–1 and acid concentration (X3) at 0.5, 1.25 and 2 M. A full quadratic regression model was established and authenticated before the variables were optimized for the highest inhibition efficiency. From the results, it was inferred that the extract concentration has the maximum effect on the inhibition efficiency followed by temperature and concentration of the acid. It was also observed that the data predicted by regression analysis had a good agreement with the data obtained from the experiments with the values of R² = 0.9946 and Adj-R² = 0.9898 for inhibition efficiency. The optimum settings for the studied parameters were found to be at temperature (50 ^◦), extract concentration (0.5 gL^–1), and acid concentration (0.5 M) to achieve the maximum inhibition efficiency of 86.19%.