Влияние добавки наночастиц ZrO2 в электролит на структуру и антикоррозионные свойства оксидных слоев, формируемых плазменно-электролитическим оксидированием на сплаве Mg97Y2Zn1

Abstract

Magnesium alloys with a strengthening long-period stacking ordered structure (LPSO-phase) offer outstanding mechanical properties, but their low corrosion resistance necessitates additional surface protection. The work investigates the influence of adding ZrO2 nanoparticles at a concentration of 1–4 g/l to the electrolyte on the thickness, structure, composition, wettability, and anticorrosion properties of oxide layers formed during plasma electrolytic oxidation (PEO) of the Mg97Y2Zn1 alloy with the LPSO-phase. It was found that during PEO, under the influence of an electric field, ZrO2 nanoparticles penetrate into the forming oxide layer and reduce its porosity. The study revealed a decrease in the quantity and size of pores near the barrier layer in places where the alloy LPSO-phase comes out to the interface with the oxide layer. Low concentrations of ZrO2 nanoparticles (1–2 g/l) reduce the corrosion rate of the alloy up to two times compared to the base case. The minimum corrosion current density icorr≈14 nA/cm2 and the highest polarization resistance Rp≈2.6 MΩ·cm2 are found in the sample formed in an electrolyte with the addition of 1 g/l of ZrO2 nanoparticles. Calculation of the barrier zone parameters of oxide layers showed that an increase in the ZrO2 concentration in the electrolyte leads to an increase in the barrier layer thickness and in its specific conductivity, which negatively affects the corrosion resistance of the formed oxide layers – the barrier zone resistance of the layer obtained by adding 4 g/l of ZrO2, drops by ~20 % compared to the base case (up to ~1 MΩ·cm2).