Gum arabic as a potential corrosion inhibitor for aluminium in alkaline medium and its adsorption characteristics

Purpose - To investigate the inhibitive effect of gum arabic (GA) for the corrosion of aluminium in alkaline (NaOH) medium and determine its adsorption characteristics. The present work is another trial to find a cheap and environmentally safe inhibitor for aluminium corrosion. Design/methodology/approach - The inhibition efficiency (%I) has been evaluated using the hydrogen evolution (via the gasometric assembly) and the thermometric methods at 30 and 40 degrees C. The concentrations of GA (inhibitor) used were 0.1-0.5 g/l and the concentrations of NaOH (the corrodent) were 0.1-2.5 M. The mechanism of adsorption inhibition and type of adsorption isotherms were proposed from the trend of inhibition efficiency with temperature, E-a, Delta G(ads) and Q(ads) values. Findings - GA inhibited the corrosion of aluminium in NaOH solutions. The inhibition efficiency increased with increase in GA concentration and with increase in temperature. Phenomenon of chemical adsorption is proposed for the inhibition and the process followed the Langmuir and Freundlich adsorption isotherms. The results obtained in this study for the %I were comparable for the two methods used and were corroborated by kinetic and thermodynamic parameters evaluated from the experimental data. Research limitations/implications - Further investigations involving electrochemical studies such as polarization method will enlighten more on the mechanistic aspect of the corrosion inhibition. Originality/value - This paper provides new information on the possible application of GA as an environmentally friendly corrosion inhibitor even in highly aggressive alkaline environments. It has not been published elsewhere.