Effect of Borreria Stachydea Leaves Extract as Green Corrosion Inhibitor on Al – Si – Mg Alloy in Simulated Seawater Environment

Corrosion inhibition effect of Borreria Stachydea leaves extract on Al-Si-Mg alloy in simulated seawater environment has been investigated at ambient temperature by gravimetric methods. Extracts of Borreria Stachydea leaves in different concentrations were used as „green‟ inhibitors. This paper reports the results obtained from the weight loss method, calculated corrosion rates, inhibitor efficiencies and temperature variations. Addition of different concentrations of the plants extracts gave considerable reduction in the weight loss and in the corrosion rate of the test samples. This apparent corrosion inhibition was associated with the protective film provided on the steel‟s surface by the complex chemical constituents of the plants extracts. The corrosion rates were found to decrease in the presence of the inhibitor, plant extract generally. The inhibition efficiency was found to increase with increasing inhibitor concentration. The effect of temperature on the corrosion inhibition of the alloy indicated an increase in the corrosion rate as temperature increased and subsequent decrease in the inhibition efficiency. The adsorption of the extract molecules on the alloy surface obeys Langmuir adsorption isotherm and occurs spontaneously. The activation energy as well as other thermodynamic parameters for the inhibition process was calculated. These thermodynamic parameters show strong interaction between inhibitor and alloy surface. Thermodynamic data calculated are suggestive of adsorption of inhibitor molecules on the alloy surface.