Inhibition Efficiency of Copper Corrosion in a Neutral Chloride Solution by Barbituric and Thiobarbituric Acids

Environmental green compounds have emerged as powerful inhibitors for metals and alloys corrosion. So, this article attempts to show that barbituric (BA) and thiobarbituric acids (TBA) are good green corrosion inhibitors for copper immersed in 0.6 mol/L NaCl. A combination of quantitative and qualitative tools were used in this investigation, such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, FT-IR spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Polarization measurements indicate that these compounds can function as mixed type inhibitors. It was found that the adsorption of these inhibitors onto the copper surface obeyed Flory-Huggins isotherm. Also, the effect of temperature in the inhibitors absence and presence was studied according to Arrhenius isotherm. Some thermodynamic functions of dissolution and adsorption processes were calculated, such as activation energy (Ea), enthalpy (ΔH), free energy (ΔG) and entropy (ΔS). The barbituric and thiobarbituric acids recorded high inhibition efficiency of copper corrosion at concentrations of 5x10 mol/L and 1x10 mol/L, respectively.