Influence of nanoparticle additions to the electrolyte on the structure, composition and corrosion resistance of oxide layers formed by PEO on cast Mg alloy

Abstract

The effect of various nanoparticles (NPs) added to the electrolyte on the composition, structure, and properties of oxide layers formed by plasma electrolytic oxidation (PEO) on a cast magnesium alloy AZ81A was studied in this work. The oxide layers were obtained by alternating adding silicon dioxide SiO2, silicon nitride Si3N4, yttrium oxide Y2O3, tungsten carbide WC, and titanium carbide TiC NPs to the electrolyte. The obtained oxide layers were studied by scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDXMA), X-ray diffraction analysis (XRD), instrumental indentation and potentiodynamic polarization (PDP). The thickness, roughness, microhardness, adhesion and corrosion resistance of the oxide layers were determined. The greatest increase in the oxide layer thickness, in its hardness and corrosion resistance was observed for TiC and WC NPs added to the electrolyte during PEO. The addition of Si3N4 NPs leads to a decrease in the oxide layer thickness and its hardness, while the corrosion resistance is comparable to the one of the uncoated magnesium alloy.

Improvement of protective oxide layers formed by high-frequency plasma electrolytic oxidation on Mg-RE alloy with LPSO-phase

“…Therefore, for Mg-RE (LPSO)-alloys to be implemented in unit and aggregate designs, additional solutions that neutralize this effect should be provided, for example, the application of protective coatings. Formation of multifunctional oxide ceramic layers on the alloy surface by plasmaelectrolytic oxidation (PEO) appears most attractive technology [21,22].…”

The effect of silica NPs incorporation on protective properties of oxide layers formed by PEO on Mg97Y2Zn1 alloy with LPSO-phase

“…It is well known that the use of various substances in the form of particles as a dispersion phase of the electrolyte under PEO is one of the most effective ways to improve the protective and functional properties of oxide coatings, as well as to increase the productivity and efficiency of the PEO technology [ [18] , [19] , [20] , [21] , [22] , [23] , [24] ]. The using of SiO 2 , ZrO 2 , TiN, Si 3 N 4 , TiO 2 , TiC, MoS 2 particles, carbon nanotubes or halloysite nanotubes as additions to the electrolyte during PEO has led to significant improvement of wear- and corrosion resistance of formed oxide layers [ 21 , [25] , [26] , [27] , [28] , [29] , [30] ]. Silicon dioxide in a nanoscale form is one of the most proven substances as an additive to the electrolyte in the PEO of aluminum, magnesium and titanium alloys.…”

Mechanical properties and corrosion resistance of Mg-RE cast alloys and their plasma electrolytic oxidation

“…However, the LPSO phase can significantly increase the corrosion rate of Mg alloys [2], therefore additional surface treatment is necessary to create an anticorrosive layer on the surface of such alloys. This problem can be successfully solved by plasma-electrolytic (microarc) oxidation (PEO or MAO) of Mg alloys [3][4][5].…”