Bark Extract of Urena lobata as Green Corrosion Inhibitor for Mild Steel in Sulphuric Acid Environment

Abstract Urena lobata bark extract (ULBE) was investigated as corrosion inhibitor for mild steel in 0.5 M H2SO4 by phytochemical method, gravimetric and surface morphological studies. Phytochemical screening revealed the presence of alkaloids, flavonoids, saponins and other phytochemicals that inhibit corrosion. The result showed that inhibition efficiency increases with concentration of the inhibitor (from 0.2 g-1.0 g) reaching maximum of 83.28% at 303 K and 24 hr immersion time. It also decreases with temperature rise from 303 K to 333 K. The thermodynamic parameters obtained support a physical adsorption mechanism and best fitted to the Langmuir adsorption isotherm. The values of activation energies obtained in the presence of the inhibitor was all higher than that of the blank solution indicating that ULBE inhibitor effectively inhibits mild steel corrosion. The inhibition process followed first order kinetics. Surface morphological studies revealed that the inhibited mild steel coupons have smooth surfaces whereas mild steel immersed in blank solution showed rough and irregular surfaces, hence confirming the inhibition ability of the inhibitor.