Inhibition of Mild Steel Corrosion by Leaves Extracts of Commelina benghalensis L In 1M HCl Solution

Abstract

The inhibition of mild steel corrosion in 1M HCl by leaves  extracts of Commelina benghalensis L was investigated using weight loss and potentiodynamic polarization techniques at room (30  and elevated temperatures of 40, 50, 60 and 70. The results of weight loss technique showed that the inhibition efficiency increased with increase in extract concentration and exposure time but decreased with rise in temperature. The maximum inhibition efficiency obtained was 81.71 % at 0.5 g/L concentration of leaves extracts. Corrosion rates decreased with increased concentration of extracts but increased with increase in temperature. Potentiodynamic polarization method results indicated that Commelina benghalensis L is a mixed - type inhibitor as it modified both the anodic and cathodic reactions in 1M HCl solution. The adsorption of the extracts on the mild steel coupons was observed to follow Langmuir and Temkin adsorption isotherms. The negative values of Gibb’s free energy of adsorption ranged from -21.35 to -23.03 kJ/mol., this suggests that inhibitor molecules were physically and spontaneously adsorbed onto the metal surface.