Electrochemical and theoretical evaluation of thiocarbohydrazide as a brass (60/40) corrosion inhibitor in 3% NaCl solution and effect of temperature on this process

Abstract

This work presents an in-depth analysis of the inhibitory effects of thiocarbohydrazide (TCH) on the corrosion behavior of brass (60Cu-40Zn) in 3% NaCl solution similar to seawater using electrochemical measurements (electrochemical impedance spectroscopy and potentiodynamic polarization), scanning electron microscopy (SEM) and quantum chemistry calculations (DFT, MC, MD). The study’s intent is to evaluate the possibility of using this molecule as an inhibitor for brass. The experimental results indicate that TCH has a very good corrosion inhibiting property toward brass in 3% NaCl. The calculated inhibition efficiency was 92.81% for a maximum concentration studied, namely, 1 mM TCH. Acceptable correlations were obtained between the inhibition efficiency and the calculated quantum chemical parameters. Studies of the temperature effect confirmed that the adsorption of TCH to the surface of brass is consistent with the Langmuir adsorption isotherm in the temperature range used. In addition, we found that this compound is characterized by a chemisorption process. Thermodynamic variables and activation energy values were determined and interpreted. The density functional theory (DFT) calculations, electrostatic potential surface (EPS), Monte Carlo (MC) and radial distribution function (RDF) simulations were achieved to obtain more insights about the adsorption mechanism of TCH towards the 60Cu-40Zn brass alloy (BA) surfaces. Moreover, the standard free adsorption energies obtained suggest strong adsorption of the inhibitor to the metal surface. The presence of TCH on active sites on the brass surface was confirmed experimentally by SEM analysis.