Synergistic effect of halide ions and polyethylene glycol on the corrosion inhibition of aluminium in alkaline medium

The corrosion inhibition of aluminium, in alkaline medium was studied at 30 and 40°C in the presence of polyethylene glycol. (PEG) using gravimetric (weight loss) and thermometric techniques. The effect of halides (KCl, KBr, and KI) on the inhibitory action of PEG was also studied. It was found that PEG acted as inhibitor for aluminium corrosion in the alkaline medium. Inhibition efficiency increased with increasing inhibitor concentration. An increase in temperature led to increase in both the corrosion rate and inhibition efficiency in the absence and presence of inhibitor and halides. Phenomenon of chemical adsorption mechanism is proposed from the values of E_a, Q _ads, and ΔG_ads^o obtained. The adsorption of PEG on the surface of aluminium was found to obey Flory-Huggins and Temkin adsorption isotherms. The synergism parameter, Si evaluated was found to be greater than unity indicating that the enhanced inhibition efficiency caused by the addition of halides is synergistic in nature. The inhibition efficiency, surface coverage and synergism parameter increased in the order; I ^-> Br^-> Cl^- showing that a joint adsorption of PEG and halide ions on aluminium, plays a significant role in the adsorption, process.