The Influence of Atmospheric Pressure Plasma Processing as Coating Pretreatment on Metal Material Surfaces

Abstract

Metal materials are sometimes coated for the purpose of improving their resistance to corrosion and their designability. Maintenance of these targeted coating effects into the long term requires proper coating pretreatment. At present, the main type of coating pretreatment is chemical conversion. Chemical conversion treatment has excellent features in respect of post-coating corrosion resistance and productivity, but requires treatment of the waste liquid, and therefore has issues in the environmental aspect. In response, this research focused on atmospheric pressure plasma processing, which does not entail any waste liquid treatment, and examined its applicability for coating pretreatment. It found that atmospheric pressure plasma processing using nitrogen could improve wettability and adhesiveness. As the underlying factors, it identified the removal of organic substances on the metal material surface and the ability to curtail an oxidation reaction on the surface. The results also suggested there was a strong possibility that the post-coating corrosion resistance of the metal materials upon improvement of their wettability and adhesiveness by atmospheric pressure plasma processing would be greatly influenced by the form of occurrence of corrosion products in the metal materials.