In this work, an attempt is made to study the effects of sunflower seed hull extract as an environment-friendly corrosion inhibitor for plain carbon steel in 1 M HCl solution. The results of the FTIR and GC analyses revealed that the sunflower seed hull extract contains compounds containing oxygen and nitrogen heteroatoms and the aromatic loops, which can be used as a useful organic corrosion inhibitor in acidic media. The inhibition efficiency was calculated using the electrochemical impedance spectroscopy and dynamic polarization. It was seen that this characterization is about 98% in the presence of 400 ppm of inhibitor. The inhibition mechanism was absorption on the metal surface and its adsorption was followed by Langmuir adsorption isotherm. For more accurate analysis, thermodynamic parameters were also calculated and analyzed. UV–vis analysis confirmed the formation of a complex on the surface between the functional groups of the utilized inhibitor and ions of the metal. The complex formed on the metal surface occupies a large area. Consequently, by blocking the surface of metal from the corrosive agents, the charge and ion transfer at the metal surface is reduced. Thus, the corrosion resistance improves.
