Potentiostatic electrodeposition was used to obtain CoCrFeMnNi high-entropy alloy (HEA) thin films on copper substrate. An electrolyte based on a DMSO (dimethyl sulfoxide)-CH₃CN (acetonitrile) organic compound was used for the HEA deposition. The microstructure of the high-entropy deposits before and after corrosion in artificial seawater was investigated by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) investigation. SEM analysis revealed that compact and uniform film consists of compact and uniform 50 nm–5 μm particles that form the HEA films. The successful co-deposition of all five elements was highlighted by the energy dispersive spectrometry investigation (EDS). Electrochemical measurements carried out in an aerated artificial seawater solution under ambient conditions demonstrated the promising potential for application in the field of anti-corrosion protection, due to the protective behavior of the HEA thin films.

In this paper, we investigate what effects heat treatment can have on potentiodynamically electrodeposited high-entropy thin film (HEA) CoCrFeMnNi alloys. We focused our study on the corrosion resistance in synthetic seawater, corroborated with the structure and microstructure of these thin films. Thin films of HEA alloys were deposited on a copper foil substrate, using an electrolyte based on the organic system dimethyl-sulfoxide (DMSO-(CH₃)₂SO)-acetonitrile (AN-CH₃CN) (in a volume ratio of 4:1), which contains LiClO₄ as electrolyte support and chloride salts of CoCl₂, CrCl₃ × 6H₂O, FeCl₂ × 4H₂O, MnCl₂ × 4H₂O and NiCl₂ × 6H₂O. Using MatCalc PC software, based on the CALPHAD method, the structure and characteristics of the HEA system were investigated, and thermodynamic and kinetic criteria were calculated. The modeling process generated in the body-centered-cubic (BCC) or face-centered-cubic (FCC) structures a series of optimal compositions that are appropriate to be used in anticorrosive and tribological applications in a marine environment. Electrochemical measurements were carried out in an aerated artificial seawater solution at ambient temperature. In the experimental media, HEA thin films proved to have good corrosion resistance and were even better than the copper substrate. Corrosion resistance was improved after heat treatment, as shown by polarization and EIS tests. The structure and microstructure of HEA thin films before and after corrosion in artificial seawater were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The XRD data showed no significant changes in the structure of HEA heat-treated thin films after the corrosion in saline media. The data obtained by polarization and ESI are supported by results from SEM-EDS. This complex study reveals that, for HEA thin films, heat treatment leads to an increase in corrosion resistance. So, this finding suggests that thermal annealing is an appropriate method for improving the corrosion performance of HEA thin films.

The viscosities of molten alkali fluorides (LiF, NaF, KF, RbF, and CsF) were measured at temperatures 373.15 K above the melting point. The viscosity has been measured by using a high-temperature oscillating viscometer modified so as to be able to determine the period and logarithmic decrement from the observed intervals between times when the oscillation passes two deflection angles and automatically calculate the viscosity. The data obtained were discussed in terms of viscous flow theory in ionic liquids. New data regarding the configurational changes in alkali fluoride ionic melts were obtained.

We investigate the corrosion behavior on the microstructure of CoCrFeMnNi high-entropy thin film potentiodynamic alloys electrodeposited on aluminum support. Using electrolytes based on dimethyformamide (DMF), (HCON(CH₃)₂), dimethylsulfoxide (DMSO, (CH₃)₂SO), an acetonitrile (AN, CH₃CN) organic system (4:1 vol. ratio), LiClO₄ in different concentrations and CoCl₂, CrCl₃ × 6H₂O, FeCl₂ × 4H₂O, MnCl₂ × 4H₂O and NiCl₂ × 6H₂O in different conditions, the HEA components were co-deposited on an aluminum foil substrate. Using the CALPHAD method and the MatCalc PC software, the structure of the HEA system under study was investigated by calculating the characteristic kinetic and thermodynamic criteria. The influence of each metal from HEA inside the solid solution zone and over the formation of the solid solution phase were obtained from the ratio between the derived parameters. The electrochemical measurements, which demonstrate that on an aluminum support the HEA thin films have lower corrosion resistance, were performed at ambient temperature in an aerated artificial solution. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the microstructure of HEA thin films before and after corrosion in artificial seawater. This complex study demonstrates that the electrodeposition of HEA thin films on an aluminum support is more difficult and that the resistance to corrosion is much lower compared to that in the previous work on HEA deposits on a copper support.