Corrosion Inhibition of Mild steel in 1N HCl Media by Acid Extract of Spathodea Campanulata Leaves

Abstract

Inhibition of corrosion of mild steel in HCl solution by Spathodea Campanulata (SC) leaf extract has been studied by gravimetric, polarization, electrochemical impedance measurements and temperature studies. Inhibition efficiency was found to increase with increasing concentration of the extract. The effect of temperature (35-75 o C) and immersion time on the corrosion behavior of mild steel in 1 N hydrochloric acid on addition of extract was also studied. The inhibitor molecules were found to get adsorbed on the metal surface obeying Langmuir, Temkin, Freundlich adsorption isotherms. Polarization studies showed that the extract of SC behaved as a very good mixed type inhibitor inhibiting both anodic and cathodic reaction. A maximum inhibition efficiency of 84.5% was obtained at an inhibitor concentration of 1.5% (v/v). Surface analysis was done by scanning electron microscope technology (SEM) to study the nature of adsorption. Keywords: Corrosion inhibitor, Mild steel, Spathodea Campanulata, Polarization, HCl medium 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3% and 1.5% v/v) and without plant extract (Blank). After 1 hour immersion in the test solution the coupons were removed washed, dried and weighed. The experiment was carried out at different immersion periods (1 Hr, 2 Hr, 5 Hr, 7 Hr, 12 Hr and 24 Hr). Weight loss was measured for all the above mentioned timings at 303K. Corrosion inhibition studies were also carried out at different temperatures (308, 318, 328, 338 and 348K). After measuring the weight loss, surface coverage (θ) and percentage inhibition efficiency (IE %) were calculated using the following formula θ = (IE % / 100);