ZrO2 coatings were deposited on graphite and titanium from an aqueous solution based on a water‐soluble precursor. A two‐step mechanism is suggested for the ZrO2 formation: generation of hydroxyl ions (OH−) at the cathodic substrate by reduction of NO3− and dissolved O2 , and then reaction of the hydroxyl ions with zirconyl ions present in the solution to form the hydroxide normalZrfalse(OH)4 , which in turn decomposes on drying to yield zirconia false(ZrO2false) . Faradaic efficiencies of 20–50% were found, attributable to reduction reactions that do not produce hydroxyl ions, as well as to formation of the hydroxide at sites removed from the cathodic substrate due to diffusion of the hydroxyl ions. The effects of current density, time, and hydrodynamic conditions on coating weight, cell voltage, temperature, and pH of the solution were studied.

Zirconia coatings were formed on graphite and titanium substrates by electrodeposition. The as-deposited coatings were amorphous and cracked during the drying stage. Sintering of the coatings on the graphite substrates caused crystallization, with formation of a variety of mixtures of the tetragonal and monoclinic ZrO2 polymorphs having nanosize crystallites. Oxidation of the Ti substrate and reaction with zirconia during the heat-treatment resulted in addition to a microstructure resembling ceramic composite coatings.