Ion implantation applications for pitting corrosion inhibition : Tungsten beam implantation of Aluminum and Nitrogen plasma ion implantation of 304L stainless steel

Author

Preston Paul Smith

Date of Award

5-1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Metallurgical Engineering

Major Professor

R. A. Buchanan

Abstract

Ion implantation has been investigated to assess the effects of the implanted species on inhibiting the chloride induced pitting corrosion of common commercial alloys. Studies are described involving the application of an emerging technology, plasma ion implantation, to implant 304L stainless steel with nitrogen, as well as ion beam implantations of aluminum 1100 with tungsten. These surface modifications can potentially be very effective in enhancing corrosion resistance by producing non-equilibrium surface alloys and/ or surface structural changes, and by conserving cost-prohibitive alloying elements. Many of the limitations of the ion beam implantation process may eventually be ameliorated by plasma ion implantation (PII), in which workpieces can be immersed in a plasma for simultaneous exposure of the entire surface. The focus of this research was to document alterations in the pitting behavior by both electrochemical and immersion techniques, and to characterize the resulting microstructure, corrosion mechanisms, and implanted species distribution.

Tungsten additions always enhance the passivity of Al, regardless of the substrate alloy or the applied dose (3 - 9 x 10¹⁶; ions/cm²;). Anodic polarization, potentiostatic, and immersion testing all indicate that the implanted tungsten acts to significantly slow pitting propagation. This improvement can be traced primarily to oxide blisters which form on the surface during pitting.

Nitrogen ions have been successfully implanted into 304L stainless steel in a uniform microwave plasma. An increase in pitting potential of up to 700 mV was measured for relatively low doses. No improvement was noted for higher doses, indicating that nitrogen doses effective in improvement of wear properties may not be effective in enhancing localized corrosion resistance. Low accelerating potentials were successfully utilized to increase the N ion concentration in the near-surface region. The lateral dose uniformity on 304L specimens exposed to N PII has been greatly improved through successive modifications of the sample holder geometry.

Recommended Citation

Smith, Preston Paul, "Ion implantation applications for pitting corrosion inhibition : Tungsten beam implantation of Aluminum and Nitrogen plasma ion implantation of 304L stainless steel. " PhD diss., University of Tennessee, 1995.
https://trace.tennessee.edu/utk_graddiss/10224