Silybum Marianum oil as green inhibitor for carbon steel corrosion in 1 M HCl solution: Electrochemical and SEM investigations

Silybum marianum oil (smo) was tested as corrosion inhibitor for carbon steel in 1 m hcl using potentiodynamic polarization (pdp),electrochemical impedance spectroscopy (eis) and scanning electron microscope (sem). the effect of temperature on the corrosion behavior of carbon steel in 1 m hcl with addition of smo was studied in the temperature range of 303-333 k. the experimental results reveal that smo has a good inhibiting effect on the metal tested in 1 m hcl solution. potentiodynamic polarization (pdp) studies clearly reveal that it acts essentially as a mixed mode of action. the protection efficiency increases with increasing of inhibitor concentration to attain 89.1 % at 3g l-1. eis results show that the charge transfer resistance rct increases with increasing of smo concentration. the change in the impedance parameters (rct and cdl) with concentration of smo is indicative of the adsorption of molecules leading to the formation of a protective layer on the surface of carbon steel. sem analysis substantiated the formation of protective layer over the carbon steel surface. it is evident from the results of this study that smo inhibits the corrosion in 1m hcl through adsorption process following the temkin adsorption isotherm. the thermodynamic data of activation are determined and discussed.