New Synthesized Guanidine Derivative as a Green Corrosion Inhibitor for Mild Steel in Acidic Solutions

A new safe corrosion inhibitor namely N-(5,6-diphenyl-4,5-dihydro-[1,2,4]triazin- 3-yl)-guanidine (NTG) has been synthesized and its inhibitive performance towards the corrosion of mild steel in 1 M hydrochloric acid and 0.5 M sulphuric acid has been investigated. Corrosion inhibition was studied by chemical method (weight loss) and electrochemical techniques include Tafel extrapolation method and electrochemical impedance spectroscopy (EIS). These studies have shown that NTG was a very good inhibitor in acid media and the inhibition efficiency up to 99% and 96% in 1M HCl and 0.5M H2SO4, respectively. Polarization measurements reveal that the investigated inhibitor is cathodic in 1M HCl and mixed-type in 0.5M H2SO4. Activation energies of the corrosion process in absence and presence of NTG were obtained by measuring the temperature dependence of the corrosion current density. Data obtained from EIS were analyzed to model the corrosion inhibition process through equivalent circuit. Comparable results were obtained by different chemical and electrochemical methods used. The adsorption of the inhibitor on the metal surface in the acid solution was found to obey Langmuir's adsorption isotherm.