Carob seed oil: an efficient inhibitor of C38 steel corrosion in hydrochloric acid

Background: The carob seed oil (CO) was tested as inhibitor of the corrosion of C38 steel in 1 M HCl by weight loss and electrochemical measurements. The extract was found to inhibit the corrosion of C38 steel in 1 M HCl. Results: The results of the study reveal that the inhibition efficiency of CO depends on its concentration and attains approximately 86.7% at 0.5 g/L. Polarization curves reveal that CO is a mixed-type inhibitor. Changes in impedance parameters (charge transfer resistance, R-t, and double-layer capacitance, C-dl) were indicative of CO adsorption on the metal surface, leading to the formation of a protective film. The effect of temperature on the corrosion behavior with the addition of 0.5 g/L of carob seed oil was studied in the temperature range of 298 to 328 K. Conclusions: Results show that the inhibition efficiency of the plant extract increases with increasing temperature, and the adsorption of the latter on the C38 steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution processes were also determined.