Engineering the surface and interface of Parylene C coatings by low-temperature plasmas

Abstract

There is a need for the development of environmentally benign processes by which to protect aluminum alloys from corrosion. Vacuum-deposited Parylene C conformal coating is a very good candidate to provide such protection due to its excellent bulk properties: its moisture barrier, high mechanical strength and thermal stability. However, its poor adhesion to most smooth or non-porous substrates has restricted its application. In this study, low-temperature plasma deposition and treatment has proved to be a powerful approach to engineer the surface and interface of Parylene C coatings. After applying a special plasma polymer coating, which acts as an inter-layer to provide good adhesion to the substrate as well as to the subsequent primer, an excellent adhesion of Parylene C coating to a smooth 7075-T6 aluminum alloy has been achieved. After the surface has been functionalized by plasma treatment, the naturally hydrophobic Parylene polymer became paintable with both solventborne and waterborne spray primers.