Psidium guajava leaf extract as green corrosion inhibitor for mild steel in phosphoric acid

Abstract

The adsorption and corrosion inhibition property of the alcoholic Psidium guajava (guava) leaf extract on mild steel in 1M phosphoric acid medium was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The studies showed that the inhibition efficiency increases with inhibitor concentration upto 800 ppm and decreases slightly at 1200 ppm. The adsorption obeys both the Langmuir and the Temkin adsorption isotherm equations. The kinetic and thermodynamic parameters were calculated and discussed. The adsorption was found to follow a comprehensive type adsorption dominated by chemisorption. Potentiodynamic polarization studies showed that the inhibitor acted as a mixed-type inhibitor. © 2015 The Authors.