Investigation of plasmaion vapor deposition (IVD) hybrid coatings for corrosion protection and plasma destruction of oral bacteria
This dissertation reports the research results obtained in investigating low pressure plasma coatings for corrosion protection of aluminum ion vapor deposition (IVD) coated high-strength steels and in studying atmospheric non-thermal plasmas for destruction of oral bacteria. The objective of investigating plasma coatings for protection of IVD coated high strength steel is to reduce damage from corrosion and prevent its hydrogen re-embrittlement that often occurs in aircraft. In this study, we completed the design and construction of a hybrid IVD/plasma coater, which has the capability of producing both aluminum IVD coatings and plasma coatings of trimethylsilane (TMS). Both IVD Al coating and TMS plasma coatings were successfully prepared by the hybrid coater. The coating properties of the resulted IVD coating and TMS plasma coating were characterized and evaluated. Corrosion property evaluation using potentiodynamic polarization technique indicated that TMS plasma coated IVD specimens showed a decrease in the magnitude of corrosion potential and a decrease in corrosion current compared to bare IVD, and thus better corrosion resistance. Corrosion test results from SO2 salt spray test showed that a similar amount of corrosion products were found with the plasma coated IVD specimens as their controls, i.e., chromate conversion coated IVD samples, and did not form visible amounts of red rust after 504 hours neutral salt fog. Hydrogen re-embrittlement testing demonstrated that TMS plasma coated IVD specimens gave better test results as compared with bare IVD samples. This result is believed to be due to the improved corrosion resistance of the TMS plasma coated IVD specimens and thus less amount of hydrogen formation as a corrosion by product. It was further found that IVD Al coating should be exposed to oxygen or air in order to create an oxide layer before organosilane coatings are applied for stronger corrosion resistance. TMS plasma coating did not cause contamination to IVD. Likewise, the application of IVD in
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