Inhibition of corrosion of mild steel in hydrochloric acid by the leaf juice of chanca piedra (Phyllanthus niruri) plant

Abstract

The inhibition of corrosion of mild steel in 0.5M, 1.0M and 2.0M hydrochloric acid solutions by chanca piedra’s juice obtained from squeezed fresh leaves and added to the acid solutions at 15ml and 20ml per litre has been studied using coupons. Corrosion inhibition was obtained. The inhibition rate appears to attenuate from about the fourth hour upwards with a transition to a constant corrosion rate presentation. This indicates a possible depletion of the corrosion inhibiting constituents following the apparent completion of the reactions that produce corrosion products that adhere to the surface of the mild steel. A maximum corrosion efficiency of 70 percent was attained. It is proposed that a higher corrosion inhibition efficiency level could be attained by concentrating the leaf juice by water evaporation from it. The mechanisms of corrosion inhibition are proposed to be by adsorption through coordinate type of linkage facilitated by dipoles presented by elements like nitrogen and oxygen found in chanca piedra’s constituents like the alkaloids. Alternatively adsorption can be provided by organic compounds containing unsaturated bonds that are prevalent in many of the chanca piedra’s constituents for example, rutin, or by organic compounds containing very large molecules like the tannins also found in chanca piedra.