Caffeine was isolated from dry green tea leaves and used as corrosion inhibitor. The aim of this paper is to study the corrosion inhibition behavior of caffeine with its different concentrations (from g/L to g/L) for CT3 steel in 1M HCl solution by the curve polarization measurements and surface examination studies. Experiment result showed that: as the concentration of caffeine increases, the inhibition efficiency increases; %IE max is approximately at concentration of caffeine g/L. | Vietnam Journal of Chemistry, International Edition, 54(6): 742-746, 2016 DOI: A study on the corrosive inhibition ability of CT3 steel in 1 M HCl solution by caffeine and some characteristics of the inhibition process Truong Thi Thao*, Hoang Thi Phuong Lan, Ngo Duong Thuy Faculty of Chemistry, Thai Nguyen University of Science, Thai Nguyen University Received 2 June 2016; Accepted for publication 19 December 2016 Abstract Caffeine was isolated from dry green tea leaves and used as corrosion inhibitor. The aim of this paper is to study the corrosion inhibition behavior of caffeine with its different concentrations (from g/L to g/L) for CT3 steel in 1M HCl solution by the curve polarization measurements and surface examination studies. Experiment result showed that: as the concentration of caffeine increases, the inhibition efficiency increases; %IE max is approximately at concentration of caffeine g/L. The experimental data from all measurements was found to fit well with the Langmuir caffeine adsorption isotherm. Calculated values of free energy of adsorption Gads are kJ/mol. It shown that, the adsorption is spontaneous and consistent with the mechanism of physical adsorption. It showed that, the adsorption is spontaneous and consistent with the mechanism of physical adsorption. As temperature increase from 298 to 318 K, the inhibition efficiency is relatively stable: decrease slightly from % down %. Calculated values of the heat of adsorption Hads are ranged from kJ/mol to kJ/mol, indicating that the adsorption of caffeine on the surface of CT3 steel is exothermic. The increasing of activation energy in corrosion process which presents caffeine g/L compared to absent caffeine proved that caffeine have corrosion occurred more difficult. Keywords. Caffeine, corrosion inhibitor, adsorption. 1. INTRODUCTION 2. EXPERIMENTAL Using plant extracts as green corrosion inhibitors is
