Advances in PSII deposited DLC coatings for use as barriers to corrosion

Abstract

Plasma source ion implantation (PSII) is a non-line of sight process for implanting complex shaped targets without the need for complex fixturing. The breakdown initiation of materials coated with diamondlike carbon (DLC) produced by PSII occurs at defects in the DLC, which expose the underlying material, thus establishing a galvanic couple between the coating and exposed material at the base of the defect. Pitting and oxidation of the base metal leads to the development of mechanical stress in the coating and eventually spallation of the coating. This paper presents current progress in attempting to mitigate the breakdown of these coatings by implanting the parent material before coating with DLC. Ideally the parent material would be implanted with chromium or molybdenum, which are known to improve corrosion resistance, however the necessary organometallics needed to implant these materials with PSII are not yet available. Here the effects of carbon, nitrogen, and boron implantation on the susceptibility of PSII DLC coated mild steel to breakdown are reported.