Plasma sprayed ceramic coatings usually have relatively high open porosity in order to provide a good corrosion protection. By using sealants the porosity values can be reduced. In this study atmospheric plasma sprayed (APS) aluminium oxide, chromium oxide and zirconium oxide coatings were sealed by a phosphoric acid treatment. After impregnation the coatings were heat treated at a curing temperature of 400°C. Phosphoric acid was found to react with the coating material during the heat treatment. Wear resistance was evaluated by rubber wheel abrasion tests and corrosion resistance by electrochemical potentio-dynamic polarization tests. Hardness values were also measured. Corrosion resistance and hardness values of sealed coatings were remarkable better in comparison to the unsealed coatings. Rubber wheel abrasion resistances of the sealed coatings were equal to those of Al2O3, ZTA, SiC and Si3N4 sintered ceramics.