Study Of Coatings Formed On Zirconium Alloy By Plasma Electrolytic Oxidation In Electrolyte With Submicron Yttria Powder Additives

Coatings with thickness 40 to 150 mu m were formed by plasma electrolytic oxidation (PEO) on the zirconium alloy Zr-1Nb (Zr-1% Nb) in the slurry electrolyte containing 9 g/L Na2SiO3 5H(2)O, 5 g/L Na(PH2O2) and 6 g/L submicron Y2O3 yttria powder during 60 min under the AC electrical mode at current densities 20; 30 and 40 A/dm(2). The surface morphology, structure, composition, and corrosion-protective ability of the formed coatings have been analyzed. At PEO current density 30 A/dm(2), a predominantly tetragonal phase of zirconia was formed in coatings. Increasing the PEO current density up to 40 A/dm(2) promoted the formation of the coating surface layer containing submicron yttria particles. Electrochemical polarization studies in 0.5% LiOH solution showed that PEO coatings demonstrated high corrosion-protective ability. The dependence of the polarization currents on the PEO current density was found to be inconsequential.