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

Plasma source ion implantation (PSII) is a non-line of sight process for im planting complex shaped targets without the need for complex fixturing. The breakdown initiation of materials coated with diamondlike carbon (DLC) pro duced by PSII occurs at defects in the DLC, which expose the underlying mat erial, thus establishing a galvanic couple between the coating and exposed material at the base of the defect. Fitting and oxidation of the base metal leads to the development of mechanical stress in the coating and eventuall y spallation of the coating. This paper presents current progress in attemp ting to mitigate the breakdown of these coatings by implanting the par ent material before coating with DLC. Ideally the parent material would be impl anted with chromium or molybdenum, which are known to improve corrosion res istance, however the necessary organormetallics needed to implant these mat erials with PSII are not yet available. Here the effects of carbon, nitroge n, and boron implantation on the susceptibility of PSII DLC coated mild ste el to breakdown are reported. (C) 1999 IoM Communications Ltd.