A process for forming a thermally and chemically inert multi-layer film on a substrate, comprising depositing a composition comprising one or more inorganic oxide material, or mixtures thereof, on the substrate such as to form a continuous layer comprising a at least partially fused inorganic oxide material； depositing a composition comprising one or more non-fluorinated silane compounds, or mixtures thereof, on the continuous layer comprising a fused inorganic oxide material such as to form a layer comprising non-fluorinated polysiloxane； depositing a composition comprising one or more fluorinated silane compounds on the layer comprising non-fluorinated polysiloxane such as to form a layer comprising fluorinated silanes bearing a fluorinated group； depositing a composition comprising one or more copolymers of tetrafluoroethylene on the layer comprising fluorinated silanes bearing a fluorinated group such as to form a layer comprising a copolymer of tetrafluoroethylene.
