Examining the effectiveness of Guava leaf extract in mitigating corrosion of aluminium in potassium hydroxide solution

Abstract

This study is on the effectiveness of guava leaf extract in mitigating corrosion of aluminium in potassium hydroxide solution. Functional groups of the extract were revealed using Fourier transform infrared spectroscopy. In addition, qualitative and quantitative analyses of the extract were carried out to ascertain the level of the phytochemicals. Effects of process variables on the effectiveness of guava leaf extract as corrosion inhibitor were determined. Then, modeling of the experimental data of inhibition efficiency of the guava leaf extract was carried using response surface methodology. In the process, modeling of the inhibition efficiency was actualized using design expert software version 11. Analysis of variance and diagnostic analysis of the model on interactive effects of inhibitor concentration, temperature and time on the inhibition efficiency were examined. Analysis of the results showed that the main functional groups of guava leaf are O-H stretch, C-H stretch, N-H bend, CH3C-H bend, C-O stretch and C-H bend. Alkaloid was found to be highly concentrated in the extract; 223.71 ±0.12 mg/100g. Tannins, flavonoids, phytates and saponins were present at moderate (concentrated) levels. Weight loss, corrosion rate, inhibition efficiency and degree of surface coverage were influenced by the inhibitor concentration, temperature and time. Quadratic model adequately described the relationship between inhibition efficiency and process variables. The predicted R² of 0.9311 is in reasonable agreement with the adjusted R² of 0.9867. Guava exhibited high inhibition efficiency. Hence, it can be used to inhibit corrosion of Al in KOH solution.