Abstract
The inhibitory strength of two amino acids namely, tryptophan (Tryp) and histidine (Hist) on the corrosion of SABIC iron (SABIC Fe) in a 0.5 M HCl solution was examined utilizing mass loss (MS), electrochemical (PDP and EIS) and theoretical studies. Density functional theory (DFT) and Monte Carlo (MC) simulation were inspected for Tryp and Hist inhibitors. All the corrosion parameters and theoretical data obtained from these studies confirm the inhibiting impact of the two amino acids. The efficacy of inhibition augment with augmentation the concentration of two amino acids from 100 to 500 ppm and reducing at elevated temperature. The effectiveness of the inhibition depends on the presence of some active centers that accelerate the adsorption process and the molar mass of the inhibitors. The inhibition efficacy of Tryp is greater than that of Hist reaching 92.09% at a concentration of 500 ppm while in the presence of Hist it is 89.37% using PDP measurements. Inhibition was demonstrated by spontaneous adsorption of Hist and Tryp on the surface of SABIC Fe according to the Langmuir adsorption isotherm. PDP curves clarified that the Tryp and Hist compounds acted as mixed type inhibitors. A variety of thermodynamic and kinetics parameters were computed and explained. SEM images demonstrate that the protective layer constructed on the surface of S– Fe in the presence of both amino acids. The results obtained from DFT are in complete agreement with the experimental work. Tryp and Hist compounds are adsorbed horizontally onto the surface of Fe (110).
•Tryp and Hist compounds are effective inhibitors of Sabic iron in 0.5 M HCl solution.•Tryp and Hist compounds considered mixed type inhibitor.•Adsorption of Tryp and Hist compounds on the surface of SABIC iron is subject to Langmuir isotherm.•Theoretical data provide in-depth understanding of the experimental results.