Thermodynamics, adsorption, and response surface methodology investigation of the corrosion inhibition of aluminum by Te
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ORIGINAL PAPER
Thermodynamics, adsorption, and response surface methodology investigation of the corrosion inhibition of aluminum by Terminalia chebula Ritz. extract in H3PO4 Deepa Prabhu1 · P. R. Prabhu2 · Padmalatha Rao3 Received: 27 May 2020 / Accepted: 11 August 2020 © The Author(s) 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 (icorr) 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
Introduction Mild steel and aluminum are the two most commonly used material as it is easily available and at a lower cost. Acid solutions are commonly used in industry where hydrochloric, sulfuric acid, and phosphoric acids are the mostly used to remove the metal oxides that are formed on the surface of metals (Solomon et al. 2010; Yüce 2020; Santos et al. 2020). * P. R. Prabhu [email protected] 1
Department of Chemistry, International Center for Applied Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
2
Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
3
Department of Chemistry, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
Over time, the frequent use of these acid solutions may cause deterioration in metallic materials. Nowadays, the industry and the academic sectors have been interested in the use of inhibitors due to their adsorption onto the surface of the metal can reduce the corrosion rate (CR), and such adsorption depends on the physical–c
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