Surface protection of steel in acid medium by Tabernaemontana divaricata extract: Physicochemical evidence for adsorption of inhibitor

For the first time, the homogeneous adsorption of a green inhibitor on the surface of steel was evidenced using energy dispersive X-ray spectral elemental mapping. Inhibition of steel corrosion in 1.0 M hydrochloric acid by Tabernaemontana divaricata plant extract and the evidences for adsorption of the inhibitor are described in this study. The inhibition characteristics of the green inhibitor were evaluated by means of weight loss and electrochemical measurements. A maximum of 95% inhibition efficiency was achieved by using 500 ppm of inhibitor. The adsorption of green inhibitor was found to obey the Langmuir's isotherm model. Further, the energy dispersive spectral mapping revealed the homogeneous distribution of the nitrogen, which indicated for the presence of inhibitor on the steel surface.