Hydrophobic fluorinated carbon coatings on silicate glaze and aluminum

Hydrophobic, adherent, and strong coatings would be desirable for the glazed porcelain insulators and aluminum conductors of electric power grids. Micron-thick films consisting of fluorinated carbon (CFn) on top of adherence layers (a-C:H on Si or Cr) were deposited on insulator pieces and aluminum, using a benign Ar/C2H2/C3F8 chemistry in a dual magnetron sputtering/plasma-enhanced chemical vapor deposition system. A wide range of process parameters was explored: pressure from I to 67 Pa, substrate r.f.-induced d.c. offset from -50 to -1000 V, and different gas ratios. Advancing and receding contact angle measurements, X-ray photoelectron spectroscopy, optical and atomic force microscopy, micro- and nano-indentation, and scratch testing were performed. Contact angles as large as 130degrees were obtained. The film F content was < 30 at.%, with clearly identified CFn groups as well as C-C cross-linking bonds. The hardness was equal to or higher than the substrate's. High pressure coatings display a rough morphology while the lower pressure ones are smooth, the morphology, as well as the chemistry, influences the wetting properties. (C) 2002 Elsevier Science B.V All rights reserved.