Interference color appearance and its aesthetic control on aluminum surface via anodizing and sputter coating

Interference colors on anodized and sputter-coated aluminum alloys were investigated. The transmittance of the thin metal film fabricated by DC magnetron sputtering strongly affected the interference colors on anodized aluminum. Appropriate balance of transmittance and reflectance of coating layer leads to the appearance of interference colors on anodized aluminum. The interference colors on anodized and sputter-coated aluminum had an angular dependence. This angular dependence strongly depended on the surface roughness of aluminum specimen. On flat surfaces, light of specific wavelengths interferes at each different angle. Conversely, due to light scattering, light of various wavelengths interferes on rough surfaces. These scattering causes the decreasing of angular dependence. Interference colors generated by anodizing aluminum before sputter-coating can appear on curved surface, making the appearance of aluminum more vivid. Surfaces of aluminum exhibiting various interference colors can be designed on the single surface using selective anodizing method.