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Centella asiatica extracts as green corrosion inhibitor for mild steel in 0.5 M sulphuric acid medium

S. S. Shivakumar and K. N. Mohana

The leaf extracts of centella asiatica(CE) was tested as green corrosioninhibitor for mild steel in 0.5 M H2SO4 by using gravimetric, polarization and electrochemical impedance spectroscopy (EIS) measurements. The data obtained from all the three methods are in good agreement with each other. Results indicate that leaf extracts of CE is a good green corrosion inhibitor for mild steel corrosion in 0.5 M H2SO4 solution. The inhibition efficiency was found to increase with increase in CE extracts concentration. A maximum inhibition efficiency of 95.08% was observed for 1200 ppm at 303K. Polarization measurements showed that the CE extracts acts as mixed type of inhibitor.Temperature studies revealed a decrease in inhibition efficiency with increase in temperature which suggests physisrption mechanism. The adsorption characteristics of CEextracts of on mild steel surface obeys Langmuir isotherm. Both kinetic and thermodynamics adsorption parameters were calculated and discussed,and SEM was used to analyse the surface adsorbed film.