Plasma-Electrolytic Oxidation of Valve Metals in Zr(IV)-Containing Electrolytes

The studies devoted to the production of Zr-containing coatings on valve metals (Ti, Al, and Mg) using plasma-electrolytic oxidation are reviewed. The coatings are formed from aqueous electrolyte suspensions containing dispersed ZrO2 particles, as well as Zr(IV) fluorocomplexes, polyphosphate, and tartrate complexes, and from Zr(SO4)(2) electrolytes. The layers that contain both zirconium oxide in either monoclinic or tetragonal modification and zirconium pyrophosphate and layers containing simple and complex zirconium phosphates are obtained. The described approaches enable one to produce protective layers and can form the basis of the technique for obtaining surface structures with a complex chemical composition, as well as coatings that contain certain compounds with specific characteristics.