Inhibition of Aluminium Corrosion in KOH Solution Using Extract of Grape Leaf as Inhibitor

Abstract

This work focused on the inhibition of aluminium corrosion in KOH solution using extract of grape leaf as inhibitor. It involved the characterization of the extract in terms of functional groups and phytochemicals. Gravimetric (weight loss) method was used for the corrosion control study. Weighed Al coupon was immersed in 250 ml open beaker containing 150 ml of 1 M KOH (without inhibitor). Also, Al coupons were separately immersed in 250ml open beakers containing 150 ml of 1 M KOH with various concentrations of the grape leaf extract. Variation of weight loss was investigated at various times (3hrs - 5hrs), and temperatures (303K – 223K), in the absence and presence of various concentrations of the inhibitor (0.6g/L - 1.0g/L). At 1hr time interval, the coupons were taken out, immersed in acetone, scrubbed with a bristle brush under running water, dried and reweighed. Then, values of the inhibition efficiency were determined. From the analysis of the experimental results, the grape leaf contains polar atoms of nitrogen and oxygen, which means that it is a suitable corrosion inhibitor. On the level of the phytochemicals, alkaloids, tannins, flavonoids and saponins are present in the leaf extract at various degrees. Corrosion inhibition of aluminium in KOH was found to be dependent on inhibitor concentration, temperature and time. Grape leaf extract displayed high level of inhibition efficiency. Optimum inhibition efficiency of grape leaf extract is 87.44%, which was obtained at inhibitor concentration of 0.79g/L, temperature of 312.57K, and time of 3.90hr. Grape leaf extract should be applied in corrosion control of Al in the alkaline solution.