Plasma source ion implantation process for corrosion protection of 6061 aluminum

Summary form only given, as follows. Describes results of an investigation of the feasibility of using nitrogen plasma source ion implantation (PSII) treatment to improve corrosion resistance of 6061 aluminum to salt water. Flat Al samples were implanted with various doses of nitrogen. The peak target potential was -30 kV and various pulse repetition frequencies and pulse lengths were investigated. Irregular, pre-machined commercial components (threaded connectors) were also implanted at the same target potential with a dose of 7/spl times/10/sup 16/ ions/cm/sup 2/. Both RF induction and tungsten filament sources were used to generate the plasma. The surface microstructures and profiles of Al and N in the flat samples were examined using transmission electron microscopy (TEM), scanning Auger microprobe, X-ray diffraction. Corrosion properties of the samples and the components were evaluated using both a 500 hour salt spray field test and a laboratory electrochemical corrosion system. The tested samples were then analyzed by scanning electron microscopy. Corrosion measurements have demonstrated that PSII can significantly improve the pitting resistance of 6061 aluminum. By correlating the analytical results with the corrosion test results, it has been verified that the improved corrosion resistance in PSII-treated coupons is due to the formation of a continuous AlN layer. It was also identified that the formation of a continuous AlN layer is mainly determined by the bias voltage and the total integrated implantation dose, and relatively insensitive to factors such as the plasma source, pulse length, or frequency.