Thick coatings of porous zirconia by anodization of zirconium in an organic electrolyte

Anodization, a traditional route to the fabrication of dense protective coatings or coatings with ordered arrays of pores, is used to fabricate thick coatings of zirconia. The initial transients in high current density that characterize the formation of a stable pore assembly are followed by a long period of gradually diminishing growth rate during which tubes of zirconia grow inwards into the Zr substrate. Following optimization of the voltage and electrolyte composition, coatings of 120 and 200 μm may be grown in 6 and 24 h. It is shown that diffusion of ions in solution towards the oxide-electrolyte interface is rate controlling, leading to parabolic growth kinetics.