Ceramic coatings by anodic spark deposition

A wide range of ceramic coatings has been deposited on metal substrates by a reaction occurring during dielectric breakdown at the anode surface in an electiochemical cell, which is accompanied by visible sparking at the anode/electrolyte interface. While the majority of work reported has been on oxide coatings deposited from aqueous electrolytes, non-oxide coatings have been deposited and non-aqueous electrolytes have been utilized to deposit both oxide and non-oxide coatings. Under normal circumstances the dielectric breakdown occurs across an anodized barrier film formed on a valve metal anode, but the process is not limited to this description. The coating is usually composed of compounds containing elements from both the anode and the electrolyte. Interest in such coatings ranges from prosthetic implants to corrosion protection, from bearing surfaces incorporating solid lubricants to catalyst carriers. The present state of understanding ol the process and its applications is presented.