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

The inherited chemical inhomogeneity in oxide layers obtained by plasma electrolytic oxidation (PEO) on the magnesium alloy MgYZn is associated to long-period stacking-ordered (LPSO) phase present in the treated alloy. This heterogeneity results in decrease of corrosion resistance and adhesion strength. The problem was solved by adding silica nanoparticles (NPs) into the electrolyte under PEO. According to the model developed, NPs which are harder than the oxide layer and being electrically charged, can be accelerated by an electric field and penetrate deep into the layer. The near-surface incorporation of NPs results in branching of the local breakdowns of vapor-gas bubbles that leads to an increase of the volumes of oxide layer and improvement of its properties.