The Role of defects which play in the process of functional degradation in environmental resisting properties of ceramic coatings

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Thin film coatings toward various types of materials have been used for protecting substrate surface from corrosion damages or adding a lot of functions to them. Till now the studies have been mainly conducted concerning mechanical and chemical properties of TiN thin film coating. Therefore in this study, basic properties such as corrosion-resisting characteristics of CVD and PVD coatings were investigated from the viewpoint of defect in coated layer and adhesion properties between coating and substrate. The roles of defects, which play in the process of functional degradation in environment resistant characteristics of coatings, were examined. And then, improvement in these characteristics of coatings by making better the adhesion state between coating and substrate is investigated.Results obtained are summarized as follows ;(1) Extremely initial stages of localized corrosion process in coated TiN thin film in 3%NaCl aqueous solution was investigated by detailed mum or urn orders observations using Atomic Force Microscope (AFM). As a result, it was observed that correlation between localized corrosion morphologies and type of defects. Moreover, crevice corrosion characteristics were controlled by the adhesion properties between thin film and substrate was recognized.(2) TiN thin film coatings used in this study were made by two different types of coating methods, that is, Plasma CVD and Dynamic Ion Mixing (DIM) method. Then, defect morphology and the initial stage of localized corrosion morphology of urn or mum orders in 3% NaCl aqueous solution was investigated by Atomic Force Microscope (AEM). As a result, difference in the types of defects and localized corrosion morphologies were dearly observed depending upon the coating methods.(3) Electrochemical AFM in-situ observation of the types of defects and initial localized corrosion process on TiN thin film made by different coating methods can be conducted under various electrochemically controlled conditions.