Inhibiting potential of hydroxypropyl methylcellulose on acid corrosion of mild steel and aluminium

Abstract

Purpose The aim of this paper is to appraise the inhibiting potential of hydroxypropyl methylcellulose (HPMC) on the corrosion of mild steel and aluminium in sulphuric and hydrochloric acid solutions. Design/methodology/approach The effects of two different corrodents on the dissolution of mild steel and aluminium were examined. Corrosion rates were determined using the weight loss technique. Inhibition efficiency was estimated by comparing the corrosion rates in absence and presence of the additive. The kinetics and mechanism of HPMC adsorption were investigated by impedance study while the anodic and cathodic partial reactions were studied by polarization measurements. Findings The results reveal that corrosion rate of mild steel and aluminium decreased with addition of HPMC. The corrosion rate and inhibition efficiency were found to depend on the concentration of the inhibitor. The polarization data indicated that the inhibitor was of mixed-type, with predominant effect on the cathodic partial reaction. electrochemical impedance spectroscopy confirms that corrosion inhibition was by adsorption on the metal surface following Freundlich adsorption isotherm via physisorption mechanism. Originality/value Hydroxypropyl methylcellulose has been studied for the first time as an inhibitor of mild steel and aluminium corrosion and the results suggest that the inhibitor could find practical applications in corrosion control in HCl and H2SO4 acid media. The findings are particularly useful, considering the fact that HPMC is a good film former and viscosity enhancer which could also be used in paint formulation.