Ta-containing coatings formed on titanium and stainless steel by plasma electrolytic oxidation and/or extraction pyrolysis

Coatings with up to 20 at.% of tantalum and phases of Ta2O5, Ta2O5·TiO2, and TiO2 have been formed on titanium in an aqueous electrolyte containing NH4[TaF6] by means of the method of plasma electrolyte oxidation (PEO). The addition of ethylene glycol into the electrolyte enables one to change the morphology and phase composition of resulting coatings. By combining the PEO and extraction–pyrolysis (EP) methods, layered coatings composed, in the upper part, of alternating elevations with predominant content of tantalum oxides and lows containing titanium oxides and calcium phosphates. The sizes of elevations and lows are about 10 μm. Layers consisting predominantly of tantalum oxides of a thickness of 3 μm have been formed on stainless steel by means of the EP method. The composition and structure of the obtained coatings make it possible to recommend their use in tests as biocompatible or bioinert media for deposition on titanium or steel implants, stents, or catheters.