A Study of the Corrosion Behavior of Engineering Mild Steel in Acidified and Hydrolyzed Extracts of Zingiber Officinale (Ginger)

Abstract

We report the use of weight loss technique in the study of the corrosion behaviour of engineering mild steel in acidified and hydrolysed corrosion media using Zingiber officinale (Ginger) extracts. Cylindrical steel rods were cut into corrosion coupons of predetermined dimensions of 15 mm by 10mm diameter. The coupons were then weighed before being suspended in situ in fours into beakers containing 10 mL, 15 mL and 20 mL of the extracts in 0.5 M and 1.0 M concentrations of H2SO4 and NaOH respectively. These setups were allowed to stand for a period of 28 days with a coupon withdrawn from each beaker after every 7 days, processed according to standard procedures before reweighing. The data of the weight loss were recorded and computations of the corrosion penetration rate using the formula; CPR=K∆W/ρA∆t were calculated. Plots of corrosion penetration rate against time, inhibition efficiency against concentration of extract and Langmuir adsorption isotherms were then plotted. The results obtained revealed that the corrosion rate profiles for passivating metals in which there is an initial sharp rise in corrosion rate, followed by a progressive decline as exposure time increased were observed. The inhibition efficiencies of the extract in the various media also showed significant increase in all the media. The Langmuir adsorption isotherms indicated that the adsorption of the molecules of the extract on the metal surface was uniformly distributed over the entire metal surface and also the adsorptive forces were strong enough to cause effective adhesion to prevent further corrosion attack. In conclusion, it was established that Zingiber officinale leaf extracts are good inhibitors of corrosion and that the inhibitive potency of the extract increases with increase in the concentrations of the extract and the corrosion media as exposure time increased, with the extract showing better inhibition characteristics in NaOH than H2SO4.