Evolution of corrosion behavior for AA7075 aluminum alloy implanted with nitrogen

This work reports the corrosion behavior of the AA7075 aluminum alloy under two different tempers (T6 and 173) after nitrogen implantation in 0.5 mol center dot L-1 NaCl solution. A combination of Electrochemical Impedance Spectroscopy and surface microstructure characterization was used to analyze the effects of nitrogen implantation on corrosion resistance. Nitrogen implantation, at 2 x 10(17) N+ ions center dot cm(-2) and 50 keV energy, induces the formation of AlN layer improving the corrosion resistance of aluminum alloys as evidenced by initial corrosion tests and a less corroded area. The evolution of the impedance indicates that the corrosion improvement vanishes over time. Implanted and unimplanted alloys show similar electrochemical parameters after 20 h immersion. However, microscopic examination shows less corrosion damage for implanted alloys after 72 h of immersion. These findings suggest that the implantation only delays the onset of corrosion probably due to degradation of AlN layer in aqueous medium. The corrosion resistance at long periods only depends on the aging heat treatment applied to the AA7075 aluminum alloy and the effect of implantation is negligible.