Molecular/electronic/atomic-level simulation and experimental exploration of the corrosion inhibiting molecules attraction at the steel/chloride-containing solution interface

The interfacial adsorption of a novel eco-friendly organic-inorganic complexes based in divalent zinc (II) cation and Tamarindus indiaca (TAM) extract molecules on the steel surface was theoretically simulated at microscopic (electronic/atomic/molecular) scales employing a combination of DFT, Monte Carlo (MC) and molecular dynamic (MD) tools and experimental examinations. The corrosion inhibition performance and mechanism were examined by electrochemical impedance spectroscopy (EIS) and polarization test. In order to characterize the TAM extract and the metal-organic complexes generation at the interface of steel/chloride-containing solutions including TAM and zinc salt (ZS), UV-vis analysis, the Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), grazing incidence X-ray diffraction (GIXRD) and contact angle (CA) measurements have been carried out. EIS results revealed the synergistic corrosion inhibition behavior of TAM 300-ZS 700 (about 96%) even after 24 h exposure. FE-SEM and GIXRD images clearly showed the formation of a uniform and protective layer on the steel substrate by exploiting the mixture of TAM and ZS exceptionally for TAM 300 - ZS 700. The highest contact angle value was attained for the TAM 300 - ZS 700 sample owing to the blocking of the substrate's active sites by inhibitor layer, confirming the successful adsorption of the inhibitor molecules on the MS, leading to corrosion mitigation. The comprehensive theoretical studies ensured the surface adsorption capacity of designed complexes giving rise to corrosion retardation impact. (C) 2019 Elsevier B.V. All rights reserved.