Abstract
Oil-impregnated nanoporous anodic oxide coating improves corrosion resistance of aluminum and its alloys with a self-healing capability to physical damages in the oxide layer. However, such performances of the oil-impregnated surface degrade by the depletion of oil within the nanoporous structures. Therefore, in order to enhance the longevity and robustness, the oil should be stably immobilized in the nanopores of anodic oxide layer against external conditions (e.g., water flow or vibration). In this work, we developed a bottle-shaped pore of anodic aluminum oxide by modulating anodizing voltage and post pore-widening process. The stability of oil in the bottle-shaped nanoporous oxide layer and its corrosion resistance were compared with those of conventional cylindrical nanoporous as well as inter-connected porous structures. Moreover, the effects of oil viscosity on the corrosion resistance and self-healing capability were also investigated. The oil-impregnated bottle-shaped pore that features a smaller pore diameter at the upper layer than at the lower layer effectively inhibits the absorption of corrosive liquids in the oxide layer, thus the corrosion resistance is significantly enhanced compared to cylindrical and inter-connected porous structures. In addition, the larger diameter at the lower layer provides the advantage to retain more oil in the porous layer which can effectively flow and cover the damaged region in the oxide layer for enhanced self-healing capability to physical damages. Since the oil with a higher viscosity shows less mobility in the bottle-shaped pores, the combination of the pore geometry and the viscosity oil possibly maximizes the corrosion resistance of the nanoporous anodic aluminum oxide coating.
Published Version
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