Acidic Corrosion Inhibition of Copper by Hydroxyethyl Cellulose

Abstract

Aims: To investigate the inhibition performance of hydroxyethyl cellulose on the acid corrosion of copper. Study Design: This study was designed to investigate the corrosion inhibition efficiency of hydroxyethyl cellulose, as well as ascertain how the additive modifies the corrosion behavior of copper in the test acid media and hence the corrosion inhibition mechanism. Place and Duration of Study: This study was carried out in the Electrochemistry and Materials Science Research Laboratory, Federal University of Technology, Owerri, Nigeria between April and September, 2012. Methodology: The corrosion inhibition performance of HEC on copper in aerated 1 M HCl and 0.5 M H2SO4acid solutions was assessed using weight loss measurements. The influence of HEC as well as HEC + KI on the corrosion behavior of copper was investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The electronic structure of the HEC molecule was modeled using density functional theory (DFT) -based quantum chemical computation, while molecular dynamics (MD) simulations were performed to illustrate the adsorption process of the HEC molecule on copper. Results: Weight loss measurements results revealed that HEC effectively inhibits copper corrosion in the studied acid media, with maximum inhibition efficiency ~95%. Maximum efficiency in 1 M HCl was obtained after 1 day of immersion and that in 0.5 M H2SO4 after 5 days. The impedance response revealed two capacitive time constants and this mechanism was not altered on addition of HEC, which functioned by adsorption onto the copper surface. The potentiodynamic polarization profile in 1 M HCl shows features of active-passive transition, whereas that in 0.5 M H2SO4 shows spontaneous passivation. These mechanisms were not modified by the inhibitor. The computational studies confirmed the corrosion inhibiting potential of HEC. The HEC/Cu adsorption energy estimated by means of molecular dynamics simulation (-55.09 kJ/mol) suggests a spontaneous physical adsorption process.