The Inhibition Characteristics of Moringa oleifera Leaf Extract on Mild Steel in Tetraoxosulphate (VI) Acid and Sodium Hydroxide Environments

Abstract

The inhibiting effects of Moringa oleifera leaves extract on the corrosion of mild steel in 0.5 M and 1.0 M both of H2SO4, and NaOH solution have been investigated using weight loss techniques. A total of 72 mild steel coupons of dimensions 10 mm x 5 mm x 5 mm were suspended using nylon strings in beakers containing the media with the leaf extract, obtained by Reflux method in concentrations of 5 ml, 10 ml, 15 ml and 20 ml respectively. The setup was allowed to stand for 28 days with a coupon withdrawn from each beaker at 7 days interval for corrosion analysis. The corrosion rate profiles showed behaviors similar to those of passivating metals that begins with a steep rise in corrosion rate and progressively decreases with increasing exposure time. However, it was noticed that at an exposure time of 14 days, the coupon in the 5 ml concentration experienced a sporadic rise in corrosion rate, which we attribute to the collapse of the passive film as a result of system agitation. The inhibition efficiency of the leaf in both media was significant, suggesting that it can be used as a green and eco-friendly alternative to the synthetic and rather hazardous inhibitors in use today. In conclusion, when compared, it was established that the inhibition potentials of the leaves were better in H2SO4 than in NaOH.