Salen type additives as corrosion mitigtor for Ni-W alloys: Detailed electronic/atomic-scale computational illustration

摘要

It is imperative to study the long-term corrosion problems of nickel alloys in acidic medium due to breakdown of their passive oxide film. Focus of this work is to enhance the knowledge of adsorption of organic additives -1-((E)-(2-((E)-(2-hydroxynaphthalen-1-yl)methyleneamino)phenylimino)methyl)naphthalen-2-ol (OPD) and 1-((E)-(2-((E)-(2-hydroxynaphthalen-1-yl)methyleneamino)phenylimino)methyl)naphthalen-2-ol (PPD) onto the surface of Ni-W alloy. Deducing the scenario of competitive adsorption of salen-type symmetrical Schiff bases (OPD and PPD) as additive molecules on Ni-W alloy surface at molecular level was studied by density functional theory (DFT), Monte Carlo simulation (MC), molecular dynamics simulation (MD) and radial distribution function (RDF) analysis. Obtained intrinsic molecular parameters from DFT shows a strong conformity to the corrosion efficiencies of experimental results. From the simulation results, PPD showed the higher polarization (650.707 a.u.), higher binding energy (E-binding = 1132.241 kJ/mol), larger negative interaction energy (E-interaction = -1132.241 kcal/mol), and negative value of adsorption energy (E-adsorption = -195.55 kcal/mol) and flat-lying spatial orientation than that of OPD. These results suggested that the role of spacers play a vital role in the adsorption process, that is, larger spacer containing PPD has strong binding interaction and high surface area coverage with Ni-W alloy surface than shorter spacer OPD. Significant findings from DFT global descriptors, MC, MD and RDF analysis ratifies the corrosion efficiencies (PPD > OPD) of experimental outcomes, which correlates positively with the larger isomeric spacer. Overall, the present study, reports offers the corrosion resistance impact of OPD and PPD additives, revealing the fact of PPD as effective one and OPD as moderate ones for Ni-W alloys, thus validating the experimental results.