Jacob Jensen with Dr. Yun Chen, Kumar Sridharan, and Dr. Todd Allen

UW-Madison Department of Engineering Physics

Naval ship design demands that corrosion of the alloys used in the hull be minimized to reduce maintenance costs and extend their lifetimes, as well as provide safety. Shot peening has long been used on metals and alloys to reduce stress corrosion cracking, while carbon ion implantation is known to affect the near-surface microhardness and wear resistance of certain alloys, while other implantations such as nitrogen ion implantation have positive effects on corrosion resistance. Testing the general and pitting corrosion benefits of these treatments led to an understanding of their potential utility in the naval applications to which this Al-alloy is generally applied. Potentiodynamic electrochemical testing and salt spray testing were performed on samples of Al 5086 with H116 temper treatment to measure resistance to ordinary and pitting corrosion in 3.5% NaCl solution (seawater concentration). Electrochemical testing was also performed with a 0.35% NaCl solution. Some samples were shot peened, others were implanted with carbon ions using a plasma immersion ion implantation facility. Based on potentiodynamic and salt spray data, shot peening had a negligible effect on corrosion. Carbon ion implantation tended to marginally inhibit corrosion while disrupting passivation characteristics. These results indicate a lack of useful general and pitting corrosion benefits from shot peening and carbon ion implantation treatments, under the present testing conditions.