Influence of Clearcoats on the Spectral and Physical Properties of Electrochemically Formed Colored Passive Layers on Zirconium

We report on the application and characterization of two commercial polymer clearcoats to electrochemically formed colored passive layers on zirconium with the aim of providing effective physical and chemical protection while allowing the unique and colorful appearance of the colored passive layers to show through. Thin layers of an acrylic automotive clearcoat ( approximately 3.5 mum thick) and an epoxy marine clearcoat ( approximately 8.5 mum thick) were applied to the colored zirconium surfaces via spin coating and were found to only slightly modify their visual properties, maintaining their vibrant colors. As clearcoats were applied, the outer surface was found to be smoother than the surface of colored zirconium, thereby reducing potential wear from friction and the adhesion of fine dirt. Clearcoat-protected samples were found to wet less easily than colored zirconium alone, thus furthering its protection against damage in ambient (surface weathering) and aqueous media (aqueous corrosion). Light microscopy experiments at a 50-400x magnification revealed the absence of any structural defects in the clearcoats. The clearcoats show the ability to protect colored zirconium from physical and chemical damage, with the automotive clearcoat exhibiting superior adhesion. Our electrochemical coloring combined with the application of clearcoats creates a novel system that possesses unique esthetic properties while simultaneously offering protection against various forms of environmental damage such as weathering or corrosion.