CORROSION BEHAVIOR OF NITROGEN-IMPLANTED ALUMINUM

Pure (99.999%) aluminum has been implanted with nitrogen using a plasm a source ion implantation process. A glow discharge plasma and a 50 kV bias were used to achieve a retained dose of similar to 10(18) N-at/c m(2). Some samples were Ar sputter-cleaned prior to nitrogen implantat ion. Auger depth profiling and TEM analysis indicated a stoichiometric AIN layer about 150 nm thick formed on the surface as a result of the nitrogen implantation process. Potentiodynamic corrosion tests perfor med in 3.5 wt% NaCl solution (seawater) indicated that nitrogen implan tation gave pure aluminum improved corrosion resistance. Without argon sputter-cleaning, nitrogen implanted samples exhibited insulating beh avior to the extent of completely suppressing the corrosion current. S putter-cleaned and nitrogen implanted samples did not exhibit the insu lating behavior, but still provided a reduction in the corrosion curre nt and a more noble corrosion potential. This work shows that a signif icant modification of the corrosion resistance of pure aluminum can be accomplished using a nitrogen plasma source ion implantation process.