ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Thermodynamics, adsorption, and response surface methodology investigation of the corrosion inhibition of aluminum by Terminalia chebula Ritz. extract in H₃PO₄

Deepa Prabhu, P. R. Prabhu, and Padmalatha Rao

Department of Chemistry, International Center for Applied Sciences, Manipal Academy of Higher Education, Manipal, India

E-mail: raghu.prabhu@manipal.edu

Received: 27 May 2020  Accepted: 11 August 2020

Abstract:

This study focuses on investigating the effect of Terminalia chebula Ritz. extract (TCE) for corrosion inhibition of Al in phosphoric acid (H₃PO₄) using potentiodynamic polarization (PDP) technique. In this study, the effect of concentration of TCE extract, the concentration of H₃PO₄ acid medium, and temperature (T) was investigated on the corrosion current density (i_corr) and inhibition efficiency (IE). The TCE was characterized by FTIR analysis, and the adsorption of TCE was justified with the help of kinetic, thermodynamic, adsorption isotherm parameters. The surface morphology study was done using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), and atomic force microscopy (AFM). The study also focuses on identifying the optimum process parameters for obtaining the maximum IE by applying the response surface methodology (RSM) and desirability function approach. The maximum IE of 83.24% was achieved at a temperature of 30 ℃, the concentration of TCE extract of 500 ppm, and H₃PO₄ acid concentration of 0.5 M. Regression analysis, Pareto chart, normal chart, main effect, and interaction effect plots are employed to acquire an in-depth understanding of process variables on IE. The IE obtained from the experiments and the predicted model is in a close match and a high value of the coefficient of determination (R² = 99.98%) displays that the generated model was able to estimate the IE accurately from the selected process variables.

Keywords: Aluminum; Terminalia chebula Ritz. extract; FTIR; PDP; Surface morphology; RSM

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01318-8

Chemical Papers 75 (2) 653–667 (2021)