Fluorocarbon coated metals and ceramics and method therefor. The metal or ceramic substrate is treated with a polar organic material to effect chemisorption of a monomolecular layer. A viscous saturated hydrocarbon coating, e.g., of petrolatum, is applied over the chemisorbed layer and is fluorinated to convert the hydrocarbon to the corresponding fluorocarbon. Such fluorocarbon coated metals and ceramics are useful for antisticking, anticorrosion and antifriction applications.
Recent trends in ceramic materials technology dictate the development of innovative products with special emphasis to their surface properties which should be compatible with aggressive environmental conditions. Such materials should have increased resistance to degradation, by lowering water absorption and pollutant deposition a swell as stain removal capability.
Fluorocarbon coatings have been widely studied because of their hydrophobic character. The presence of –CFx(1≤x≤3) groups (especially –CF2) increases the wetting angle in contact with water, which can reach values greater than 150 ° . Many fluorocarbons have been proposed as precursors for PECVD processes such as C2 F6,CF4. .Decomposition ofthese gasesin RF discharges leads to the production of CFx radicals, which are the precursors of the polymer film, and fluorine atoms, which etch the material surface . The total depo sition rate is there sult of these two competitive processes . The addition of H2in a mixture of hydrocarbons has been also suggested be cause it reacts with fluorine atoms, eliminating thus the etch ing process. Moreover H2 abstracts F from CFx radicals causing lower F/C ratio in the coating which affects the hydrophobic character of the surface. The relative densities of the species in the discharge and the properties of the deposited film depend on the process para-meters, as the feeding composition, the total pressure and the rfpower.
The purpose of the present work is to develop a plasma based process for waterproofing ceramic surfaces typically applied as construction materials.
In order to achieve this goal, Plasma Enhanced Chemical Vapor Deposition of fluorocarbon films through C2F6/H2 discharges was applied aiming at the reduction of water absorption and the development of coatings that are stable against time and aggressive conditions. More precisely, the effect of the total gas pressure and the deposition time on the deposition rate , the chemical composition and the hydrophobic character of the coatings were examined. The deposition time was chosen also as a parameter in order to investigate the stability of the coatings at a period of 4 months after the deposition