Aqueous extract of Ipomoea carnea leaves as green corrosion inhibitor for mild steel in pickling paste

The inhibitor efficiency increased from 50% to 66%. In mixtures of different proportions of HCl (4N) and H2SO4 (4N), Ipomoea carnea showed 61% to 68% protection. The inhibitor efficiency of Ipomoea increased with increase in time of application. The rate of dissolution increased with temperature. Results also show that inhibitor maintained its effectiveness over entire range of temperature. Corrosion current reduced with time both in uninhibited and inhibited paste. In uninhibited paste, the reduction in current was 11 ma in 1 hour while in inhibited paste it was 14 ma in 1 hour. The inhibitor has anodic polarization effect and it polarized mild steel by 10 mV whereas the cathodic polarization was less and it polarized mild steel by 6 mV. Thus, the inhibitor is mainly an anodic inhibitor.