Alloys with deposited nanoparticles on the surface have an advantage over alloys coated with a thin layer of unstructured oxide. The preparation of metal oxide structures is effectively carried out under the action of an electric current in a medium of hydrophobic and hydrophilic ionic liquids (ILs). ILs have an optimal electrical conductivity (if necessary, it can be changed by adding water or inorganic salts) and are "green" solvents. These properties ensure their potential application in the synthesis and deposition of nanoparticles. Nanostructures not only exhibit catalytic properties, but also contribute to the corrosion resistance of various alloys.

The surface properties of the alloy Co₇₅Si₁₅Fe₅Cr_4.5Al_0.5 with a modified oxide layer containing nanostructures were compared with the properties of the “natural” oxide coating. Comparison was also made with the properties of an oxide-free surface.

The corrosion behavior of an alloy modified with nanostructures compared to the unmodified sample was studied using potentiodynamic polarization measurements. Changes in the surface morphology after pretreatment were determined using scanning electron microscopy (SEM) and energy dispersive analysis (EDS). The crystallization temperature of the alloy is 529 ºС according to data obtained by differential scanning calorimetry (DSC).

Different conditions of preliminary exposure of the initial amorphous cobalt alloy Co₇₅Si₁₅Fe₅Cr_4.5Al_0.5 in a hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide makes it possible to increase the corrosion resistance of the alloy due to a change in the surface morphology.

In the formation of nanostructures, the conditions for their production play a special role: the value of the current density, the time of exposure, the composition of the electrolyte — a pure hydrophobic ionic liquid, or the ionic liquid with additives of inorganic salts.

The resistance of the alloy to corrosion can be increased due to the formation of a nanostructured oxide layer (nanocells) on the surface (Shown in Fig.).

The best anti-corrosion protection in a chloride solution (Ringer's solution) is provided by alloys coated with nanostructured oxide during preliminary anodic oxidation in IL - BmimNTf₂. In the case of a surface represented by a nanocellular structure, the best stability was found when nanostructures were obtained by anodic oxidation in a Li₂CO₃ salt solution with a concentration of 0.02 M in Bmim NTf₂ IL. The size of the nanocells did not affect the result, showing the same resistance to corrosion for cells with a diameter of 100 nm and 150 nm.

Figure. Voltammograms observed for different electrode surfaces in ionic liquid BmimNTf₂.