Application of Xylopia aethiopica Seed Extract as Aluminium Alloy Corrosion Inhibitor in 0.75 M KOH Alkaline Solution

Corrosion phenomena, control and prevention are unavoidable scientific issues that should be
addressed due to increase of technological development. Aluminium (Al) is one of the most abundant
elements found in the earth’s crust. The applications site of Al makes it to yield corrosion attack
despite its corrosion resistance. The aim of alloying is to enhance the desired properties possessed
by the Al. Plant extracts are rich source of naturally synthesised chemical compounds that can be
extracted by simple procedure. The present study investigated the corrosion inhibition of Al alloy in
0.75 M KOH solution at room temperature using Xylopia aethiopica seed extract. The gravimetric
technique was employed in the study. It was revealed that the presence of the spice extract in the test
solution retards the corrosion rate. The calculated inhibition efficiency from the inhibitor surface
coverage was observed to increase linearly with the inhibitor concentration. The consideration of the
Langmuir adsorption isotherm indicated that the mechanism of adsorption is Physisorption. Temkin
isotherm models explained that there were lateral attractions of the inhibitor molecules on the Al alloy
surface. Flory-Huggins isotherm model confirms that there is bulky displacement of water molecules
on the metal surface due to the presence of the inhibitor molecules. This depicts that the spice
constituents clustered on the Al alloy surface preventing contact with the corrosive environment.