Novel Treatment of Anodized Aluminum Components

Aluminum is a staple of worldwide industry and commerce. This lightweight and completely recyclable metal is used in packaging, consumer products, energy, transportation, aerospace, construction, defense applications and more. Improvements in coating and finishing technologies has led to protection and coloring improvements further broadening the utilization of aluminum. The anodizing process is a coating technique which imparts a hard, abrasive, and heat-resistant oxide finish (alumina) to aluminum. However, traditional hard anodized aluminum products are still

not suitable for exposure to certain chemicals or the corrosive dishwashing processes.

Innovators at UNH have developed a technique which provides an improved hard-coating for anodized aluminum substrates. It is known that alumina coatings can have reduced chemical resistance, especially in high pH environments. This is due to the inherent non-crystalline, amorphous forms of aluminum oxide produced by traditional anodizing. To address this issue, the innovators have demonstrated a process in which lithium is incorporated into the anodized aluminum leading to improved chemical resistance. Here, an anodized aluminum substrate is simply immersed into a water-soluble solution consisting of lithium and a suitable diketone such as acetylacetonate. In this process, a portion of the aluminum ions are exchanged for lithium. Following immersion in the lithium/diketone solution, the substrate is simply rinsed and dried. The replacement of aluminum with lithium improves the resistance of the substrates. The corrosion resistance of the new treatment was tested in the laboratory showing a 10-fold improvement over the untreated surfaces.

The significant advantage offered by this novel process is the delivered improvement in the corrosion resistance of the lithium infused coating. The method is facile and can be performed at low temperatures. The result is an anodized aluminum substrate that is suitable for use in a dishwasher, or autoclave and can be exposed to corrosive environments while still maintaining the abrasion and heat resistance of provided by the traditional anodizing process. Further, this process is dye and nickel free making the improved substrate suitable for cookware. The process is low cost and easy to scale up into current coating processes.

Dale Barkey, Ph.D, has been a professor of Chemical Engineering at the University of New Hampshire since 1987. Dr. Barkey received his Ph.D. in Chemical Engineering from the University of California at Berkely, his M.S. in Chemical Engineering from the University ofCincinnati, and his B.S. in Chemistry from Clark University. Dr. Barkey has served on several Technical Advisory Boards in the anodized aluminum and micromachining industries.