Evaluation of metal ion release and corrosion resistance of ZrO2 thin coatings on the dental Co-Cr alloys

Objectives. The aim of this study was to determine if electrolytic ZrO2 thin coatings increased the corrosion resistance and decreased the metal ion release of dental cobalt-chromium alloys. Methods. Dental Co-Cr alloys were electrolytically deposited with ZrO2 ceramic coatings using a 0.0625 M ZrO(NO3)(2) solution, at various potentials, for 500 s. The electrolytic ZrO2 gel-coated specimens were annealed at 723 K for 1 h in air. Scanning electron microscopy (SEM) was used to observe the morphology of the ZrO2 ceramic coatings on Co-Cr alloys. A dynamic polarization test was used to compare the corrosion resistance of the ZrO2 coated and uncoated Co-Cr alloys in artificial saliva. Metal ion concentrations were determined with graphite furnace atomic absorption spectroscopy (AAS). Results. The SEM micrographs showed that the Co-Cr alloy can be coated with zirconia oxide at -0.7 V more homogeneously and more completely than at -1.5 V. The polarization curves indicated that the ZrO2 coating on Co-Cr alloys annealed at 723 K for 1 h in air exhibited better corrosion resistance in artificial saliva. The results of the AASs showed that the ZrO2-coated Co-Cr alloys decreased chromium ion release levels, as compared with the uncoated Co-Cr alloys. The scratch test indicated a good bond strength between the ZrO2 and Co-Cr alloy Significance. The electrolytically deposited ZrO2 coatings on Co-Cr alloys may improve the corrosion resistance and decrease the release of metal ions. It is suggested that the electrolytic ZrO2 coating method could have a widespread application in dentistry in the future. (C) 1999 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.