Comparative Effect of Concentration and Exposure Time on Corrosion Inhibition of Alkaloids and Tannins Extracts of Jatropha Curcas and Parkia Biglobosa on Mild Steel in Acidic Media

Comparative corrosion inhibition of mild steel in 0.5 H2­SO4 by the total alkaloids and tannins extracted from Parkia biglobosa seed bark and Jatropha curcas stem bark was investigated using gravimetric method at 300C. Results showed that these phytocompounds inhibit the corrosion process of mild steel in the test solution and the inhibition efficiency depends on the concentration of the alkaloids and tannins as well as the exposure time. Their adsorption was found to obey the Temkin and Langmuir adsorption isotherms and this suggested that the inhibitor molecules have been spontaneously adsorbed onto the surface of mild steel through a physical adsorption mechanism. The inhibition efficiency is markedly higher in addition of alkaloid extracts when compared with that of tannins extracts. The inhibition efficiency increased with an increase of inhibitor concentration but decreased with exposure time. Keywords: Corrosion, Inhibition, Mild steel, Alkaloids, Tannin