Understanding corrosion inhibition mechanisms—experimental and theoretical approach

Abstract

We describe a combined electrochemical and first principle density functional study to probe the corrosion inhibiting and adsorption behavior of methionine (Met) and phenylalanine (Phe) on polycrystalline and nanocrystalline iron in acid media. Met functioned as a better inhibitor for both Fe microstructures, and was more favorably adsorbed on the nanocrystalline surface. The nanocrystalline surface however diminished adsorption of Phe. The comparable values of our computed physisorption energies (294.2 kcal mol 21 and 286.6 kcal mol 21 for Phe and Met respectively) as well as the stable adsorption orientations of both molecules on Fe suggest a controlling influence of a soft epitaxial adsorption mechanism in which C, N, O, S atoms of the molecules align with epitaxial grooves on the Fe lattice. The significant contribution of physisorptive interactions also correlates with the similarity in experimental inhibition efficiencies on polycrystalline Fe (Phe = 73% and Met = 82%), though for Met the thiol group imparts an added ability for covalent interaction with Fe, which accounts for the higher efficiency. Furthermore, we have related the diminished inhibition efficiency of Phe on the nanocrystalline Fe surface to disruption of the epitaxial patterns on the lattice as the surface becomes increasingly defective, leading to weaker adsorption. The improved efficiency of Met on the nanocrystalline surface is related to scaling up of the covalent interactions around defect sites. Our theoretical conclusions are validated by the consistency with our experimental findings.

Inhibitory Action ofFuntumia elasticaExtracts on the Corrosion of Q235 Mild Steel in Hydrochloric Acid Medium: Experimental and Theoretical Studies

“…Accordingly, the plots obtained for FE are linear, in each case. This position increased the degree of surface coverage [42]. In order to quantify the interaction between the molecules under study and the Fe surface, the adsorption energy (E ads ) of each system was calculated using the equation [43]:…”

Excellent Anticorrosion Behavior of Ruta Graveolens Extract (RGE) for Mild Steel in Hydrochloric Acid: Electro Analytical Studies on the Effect of Time, Temperature, and Inhibitor Concentration

“…EIS technique is widely used to determine the metal/solution and interface behavior and kinetics of the electrochemical processes in the absence and presence of an inhibitor [20]. The corrosion at the metal/solution interface is controlled by charge transfer resistance [21][22][23].…”

Density Functional Theory of Mild Steel Corrosion in Acidic Media Using Dyes as Inhibitor: Adsorption onto Fe(110) from Gas Phase

“…Quantum chemical methods have already proven to be very useful in determining the molecular structure as well as elucidating the electronic structure and reactivity which could be practical in designing novel high-efficiency inhibitors by quantitative structure-activity relationship (QSAR) method [16][17][18][19]. These DFT-based quantum-chemical computational simulations of suitable models have made this prevailing tool increasingly available to corrosion scientists for theoretical investigation of corrosion inhibition mechanism.…”