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[Display omitted] • Thermal pre-oxidation effects on passive film properties studied on stainless steel. • Combined surface analytical and electrochemical approach applied with closed transfer. • Thermal pre-oxidation improves corrosion resistance at active/passive transition. • Thermal pre-oxidation promotes the enrichment of molybdenum and chromium. • Thermal pre-oxidation enhances growth of the inner layer after anodic passivation. A combined X-ray photoelectron spectroscopy, time-of-fight secondary ion mass spectrometry and electrochemical approach was used to investigate the mechanisms of molybdenum and chromium enrichment of a passive film formed on a model austenitic stainless steel single crystal in aqueous acid media and the effect that thermal pre-oxidation at 250 ° C plays in the composition, thickness and stratification of the film. A clean FeCrNiMo (1 0 0)-oriented surface, prepared under ultra-high vacuum (UHV), was exposed to ultra-low pressures of oxygen at 250 ° C, forming a thin oxide film, rich in iron and chromium, as well as containing molybdenum. An argon-filled glovebox, directly attached to the UHV system, allowed for electrochemical alterations to be carried out without exposure to ambient air. After being held at open circuit potential for 30 min, hydroxylation of chromium and molybdenum was promoted, with a marked enrichment of both elements in the oxide film. A distinct bilayer film was observed. Anodic polarisation resulted in a significant growth of the inner layer and further enrichment of chromium. Pre-oxidation at 250 ° C, using an ultra-low pressure of oxygen, was found to promote protection against transient active dissolution during anodic passivation, and to cause enrichment of molybdenum in the outer layer of the passive film. [ABSTRACT FROM AUTHOR]

• PANI coating on mildsteel is reported in sodium-potassium tartrate (Na-K Tartrate) and benzoic acid in alcohol-water (BAW) system. • A new composition of the BAW system is optimized and used for aniline polymerization for the first time. • The PANI coating formed in Na-K Tartrate and BAW electrolyte is a pore-free, compact, and fine-grained nanostructured. • The new electrolyte systems do not show an anodic peak during the cathodic scan indicates superior cyclic stability. Polyaniline (PANI) is extensively researched as a corrosion protection coating for mild steel (MS) against acidic and neutral media. Corrosion inhibition performance of PANI coating on MS depends on the electrolytic solution employed for polymerization. In this study, the electropolymerization of aniline onto MS using sodium potassium tartrate (Na-K tartrate) and benzoic acid in the alcohol-water (BAW) medium is reported. The composition of BAW system was optimized and used for electropolymerization of aniline for the first time. The results showed the formation of a passive yet electro-conductive layer before the polymerization initiated. A compact layer with a fine structured PANI coating in both media was obtained. Cyclic voltammetry (CV) produced a stable PANI coating without showing anodic current in the cathodic scan. The concentration of aniline and electrolytes were optimized for better coating conditions. The prepared PANI coating was characterized by Fourier-transform infrared (FTIR) spectroscopy, Ultraviolet-visible (UV–vis) spectroscopy, Scanning electron microscope (SEM) in combination with energy dispersion spectrometer (EDX) and X-ray diffractometer (XRD). The results of PANI coating in Na-K tartrate and BAW medium are compared with a standard PANI coating prepared in oxalic acid medium. The inhibition efficiencies of PANI coating obtained in Na-K tartrate and BAW were estimated to be 82.5 % and 99.99 %, respectively in 0.1 M NaCl solution. [ABSTRACT FROM AUTHOR]