Experimental and computational explorations for the inhibitive performances of synthesized green surfactants against the corrosion of copper in nitric acid

The inhibitory characteristics of two recently synthesized biosurfactants based on amino acids, namely sodium Nhexadecyl glycine (I) and sodium N-hexadecyl valine (II), concerning copper corrosion in 1.0 M HNO3 were studied at variance of temperatures. FTIR analysis was utilized to identify the chemical structures of both synthesized biosurfactants. Various techniques were employed in this study. According to the results, the synthesized biosurfactants were played as proficient inhibitors for copper corrosion and their inhibition efficiencies (% IEs) were concentration- and structure-dependent with respect to them. At a concentration of 400 mg/L of the synthesized biosurfactants and at 298 K, the average% IE was found to be 90% for biosurfactant I and 85% for biosurfactant II. The gained higher% IEs were suggested to as a result of the potent adsorption of these biosurfactants on the surface of copper and the type of adsorption was discovered to be physical and followed Langmuir adsorption isotherm. The obtained findings signified that the synthesized biosurfactants exhibited mixed-type and interface-type inhibitors. The thermodynamic and kinetic parameters were assessed and discussed. Furthermore, the kinetics of corrosion of copper as well as its inhibition were also investigated. The density functional theory (DFT) and molecular dynamics (MD) simulations emphasized the inhibitory mechanism of the examined biosurfactants and proved the adsorption of the biosurfactants' molecules on the copper surface. Theoretical modeling also demonstrated that the biosurfactant I exhibited a greater% IE compared to biosurfactant II. The experimental results gained from all employed measurements are largely reliable with each others and are in a good consistent with the theoretical studies signifying the validity of these results.