title: Air-Impregnated Nanoporous Anodic Aluminum Oxide Layers for Enhancing the Corrosion Resistance of Aluminum.
abstract: Nanoporous anodic aluminum oxide layers were fabricated on aluminum substrates with systematically varied pore diameters (20-80 nm) and oxide thicknesses (150-500 nm) by controlling the anodizing voltage and time and subsequent pore-widening process conditions. The porous nanostructures were then coated with a thin (only a couple of nanometers thick) Teflon film to make the surface hydrophobic and trap air in the pores. The corrosion resistance of the aluminum substrate was evaluated by a potentiodynamic polarization measurement in 3.5 wt % NaCl solution (saltwater). Results showed that the hydrophobic nanoporous anodic aluminum oxide layer significantly enhanced the corrosion resistance of the aluminum substrate compared to a hydrophilic oxide layer of the same nanostructures, to bare (nonanodized) aluminum with only a natural oxide layer on top, and to the latter coated with a thin Teflon film. The hydrophobic nanoporous anodic aluminum oxide layer with the largest pore diameter and the thickest oxide layer (i.e., the maximized air fraction) resulted in the best corrosion resistance with a corrosion inhibition efficiency of up to 99% for up to 7 days. The results demonstrate that the air impregnating the hydrophobic nanopores can effectively inhibit the penetration of corrosive media into the pores, leading to a significant improvement in corrosion resistance.
authors.affiliation: Department of Mechanical Engineering and ‡Department of Chemical Engineering and Materials Science, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
authors.forename: Chanyoung
authors.initials: C
authors.lastname: Jeong
authors.affiliation: Department of Mechanical Engineering and ‡Department of Chemical Engineering and Materials Science, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
authors.forename: Junghoon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Mechanical Engineering and ‡Department of Chemical Engineering and Materials Science, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
authors.forename: Keith
authors.initials: K
authors.lastname: Sheppard
authors.affiliation: Department of Mechanical Engineering and ‡Department of Chemical Engineering and Materials Science, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
authors.forename: Chang-Hwan
authors.initials: CH
authors.lastname: Choi
mesh_terms: D000388:Air; D000535:Aluminum / Q000737:chemistry*; D000537:Aluminum Oxide / Q000737:chemistry*; D003343:Corrosion; D004566:Electrodes; D057927:Hydrophobic and Hydrophilic Interactions; D008855:Microscopy, Electron, Scanning; D058608:Nanopores
chemical_list: D000535:Aluminum; D000537:Aluminum Oxide