Corrosion inhibition of steel in sulphuric acid using Ferula Assa foetida L. extract as an eco-friendly inhibitor: Experimental and computational study

• The MD simulation was done for the adsorption of Ferula Assa foetida L. extract. • The increase in the steel corrosion resistance was 84-88%. • Based on PDP results, The inhibition efficiency rose to 89 %. The effect of Iranian Ferula Assa foetida L. (FAFL) extract as an eco-friendly inhibitor on the corrosion rate of steel in a 1 M H 2 SO 4 solution was investigated, in this new study. Several tests such as electrochemical impedance spectroscopy (EIS), mass loss, and Tafel polarization were performed to evaluate the corrosion performance of carbon steel in the absence and the presence of the inhibitor. The corroded samples were studied using field emission scanning microscopy (FESEM) and X-ray diffraction (XRD) techniques with and without the inhibitor. The results showed that the FAFL extract decreased the corrosion rate of the steel substrates by 74–89%. The minimum corrosion rate observed for the steel when exposed to FAFL extract was recorded at 0.0108 mA/cm 2 . Additionally, the enhancement in the corrosion resistance of the steel was approximately 84–88%, as indicated by the results obtained from EIS. The FAFL extract acted as a mixed inhibitor, conforming to the Langmuir model when attached to the surface. FESEM images displayed that the least corrosion attacks happened when the concentration of the FAFL extract was at an optimal level with a value of 0.6 g L -1 . XRD patterns revealed that the hydrated iron oxide was the primary corrosion product on the surfaces; however, in the presence of the inhibitor, FeS was also formed on the corroded surface. Additionally, molecular dynamics simulation was used to theoretically evaluate the inhibition behavior of the FAFL extract. Quantum calculations indicated that the narrow energy gap of the Neoisolongifolene, 8-oxo- (N) molecule, one of the main inhibitor components supported the highest adsorption on the surface with a value of –139.15 kcal mol -1 .