Electrochemical and computational aspects of surface interaction and corrosion inhibition of mild steel in hydrochloric acid by Phyllanthus amarus leaf extract (PAE)

Phyllanthus amarus leaf extract (PAE) has been investigated as a corrosion inhibitor for mild steel in 1 M hydrochloric acid. Electrochemical impedance spectroscopy and potentiodynamic polarization technique were used to monitor the inhibition behaviour of PAE for the system under investigation at different exposure time (1 h, 2 h) and temperatures (303 K, 308 K and 313 K). The inhibition capacity of PAE was observed to be increasing with increasing concentration. As the extract components got adsorbed on the metal surface, inhibition efficiency also increases and finally reached 95% at 303 K. The rise in temperature affected the inhibition efficiency adversely. Weight loss studies carried out at different exposure time also revealed the inhibition efficiency of PAE. To understand the contribution of the major component in the inhibition potential of the extract computational calculations corresponding to phyllanthin was made. The quantum chemical parameters well explain the effect of structural features on the electron donating ability of phyllanthin. The adsorption mode of PAE was found obeying Langmuir adsorption isotherm.