Corrosion inhibition through nitrogen implantation into aluminum by ion beam and plasma source ion implantation

Nitrogen alloying into aluminum by conventional techniques has shown improved corrosion resistance in chloride environments. In this investigation, two relatively new approaches for nitrogen surface alloying were studied, Ion Beam Implantation (IBI) and Plasma Source Ion Implantation (PSII).

Wrought commercially pure aluminum, Aluminum Association number 1100, was chosen as the target material for implantation. Nitrogen ions at fluences on the order of 3x10¹⁷ N atoms/cm² were implanted into the 1100 aluminum samples. The effects of polishing procedures, mainly automatic vs. manual polishing, on the corrosion resistances of control and nitrogen implanted samples were evaluated. The effects of the two different ion implantation processes, IBI and PSII, on the corrosion resistance were also studied.

The corrosion tests, anodic polarization and constant potential tests, were conducted in nitrogen-deaerated 1.0 wt.% NaCl at pH=7. The pit propagation rate was found to be greatly inhibited on the automatically polished samples implanted by the IBI process, followed by the manually polished samples implanted by the IBI process. Samples implanted by the PSII process also showed marginal improvement in pit propagation resistance, but their performance could not be directly compared with that of the IBI samples due to differences in implantation parameters.