Nitrogen plasma source ion implantation for corrosion protection of aluminum 6061-T4

It is established that nitridation of aluminum (Al) 6061-T4 by plasma source ion implantation (PSII) can dramatically enhance the pitting corrosion resistance of this alloy in marine environments (i.e., chlorine-ion-bearing aqueous solutions or humid atmospheres). Corrosion tests and microstructure analyses establish that the mechanism for successful passivation against chloride-induced pitting corrosion involves the formation of a multilayered microstructure, including the presence of a continuous layer of aluminum-nitride (AlN). Important process variables are the implantation voltage and the nitrogen dose (or total implantation time), as these two variables establish the implanted nitrogen concentration. Too high or too low an implanted nitrogen concentration will not yield the continuous AW layer required for good corrosion resistance. PSII is attractive for this application as it provides for uniform, conformal implantation of irregularly shaped objects without masking, beam rastering, or object rotation.