On The Generation of Interferometric Colors in High Purity and Technical Grade Aluminum: An Alternative Green Process for Metal Finishing Industry

Metal finishing industry is one of the leading pollutants worldwide and green approaches are urgently needed in order to address health and environmental issues associated with this industrial activity. Herein, we present an environmentally friendly approach aimed to overcome some of these issues by coloring aluminum through biomimetic photonic films based on nanoporous anodic alumina distributed Bragg Reflectors (NAA-DBRs). Our study aims to compare the macroscopic and microscopic differences between the resulting photonic films produced in high purity and technical grade aluminum in terms of color features, appearance, electrochemical behavior and internal nanoporous structure in order to establish a solid rationale toward optimal fabrication processes that can be readily incorporated into industrial methodologies. The obtained results reveal that our approach, based on a rational galvanostatic pulse anodization approach, makes it possible to precisely generate a complete palette of colors in both types of aluminum substrates. As a result of its versatility, this method could become a promising alternative to substitute conventional coloring processes currently used in metal finishing industry, which employ highly toxic and degradable chemical compounds, and expand the use of these photonic films to other sophisticated applications such as UV/NIR protective coatings for aerospace engineering. Crown Copyright (C) 2015 Published by Elsevier Ltd. All rights reserved.