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|Ceramic coatings by electrodeposition in molten salt baths|
|N. VANCASTER and G. MOORTGAT
Centre de Recherches de l’Industrie Belge de la Céramique
Centrum Voor Wetenschappelijk Onderzoek der Belgische Keramische Nijverheid (B)
In the technique of electrodeposition in molten salt baths a coating is formed by diffusion through the surface of the part to be coated which is also the cathode. In general, the anode is the crucible containing the salt bath. The material to be deposited is present as a salt in the bath which allowing formation of complex molecules with the solvent. The operating temperature depends on the nature of the salt. The applied current is generally pulsed to allow uncharged species to diffuse into the interface without saturating the surface of the cathode. Furthermore, pulsed currents allow recovery of the initial activity of the electrolyte.
By controlling the charge density applied, it is possible to control the speed of deposition and the microstructure of the ceramic deposit. The thickness of the coating can be monitored by measuring the current. The density of the coating depends on the voltage applied, on crystallisation of the coating material and on the experimental conditions.
In particular, the electrodeposition technique has a number of advantages for the production of ceramic coatings on substrates of complex shape.
Composite coating Y/Zr obtained by pulsed currents (250 µm)
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