TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Product: The product further comprises coating (II) comprising electrically conductive material, overlying the substrate, and coating (I) overlying coating (II). The product further comprises a diffusion media overlying the coating. The diffusion media comprises fibers extending though the coating. Coating (I) is formed over a flat substrate, followed by formation of a gas flow field in the substrate. The flow field comprises lands (64) and channels (62). Coating (I) is only over the channels. The coating is post-treated to add polar groups prior to forming the gas flow field. Preferred Component: The fuel cell component is a bipolar plate having an anode side and a cathode side. The coating is over the anode side and the cathode side. The mean thickness of the anode side is 15% or more than the mean thickness of the coating on the cathode side.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Material: The coatings further comprise an electrically conductive material containing gold, silver, ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum, rare earth metals, their alloys, polymeric carbon, and/or graphite. Preferred Gas: The other gas comprises oxygen.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Groups: The polar group comprises hydroxyl, halide (chloride), carboxyl, ketonic or aldehyde function group. The carbon chain has 1-4 carbon atoms. The carbon chain is linear, branched or cyclic. The coating comprises a compound containing Si-O group(s) and Si-R group, where R is (un)saturated carbon chain. The molar ratio of Si-R group to Si-O group is 1/8 to 1/2. Coating (I) further comprises polar groups to improve the hydrophilicity. The siloxane is of formula: R2SiO, where R is alkyl, linear, branched or cyclic carbon chain, or (un)saturated carbon chain. Preferred Material: The precursor gases comprise a silicon-containing material of formula: R2-Si(-R1)(-R3)-O-Si(-R4)(-R6)-R5.R1-R6=H, O, Cl, or (un)saturated carbon chain.Preferred Coating: Alternately, The coating includes nanoparticles having a size of 1-100 nm and comprising the siloxane compound. The nanoparticles have a nodular shape. The coating is sufficiently porous to allow fibers of a diffusion media to extend. The coating is treated to add polar groups, by exposing the coating to a plasma comprising oxygen (ions). Coating (I) is formed by physical vapor deposition, chemical vapor deposition, thermal spraying, sol-gel forming, spraying, dipping, brushing, spinning on, or screen printing.    TECHNOLOGY FOCUS - POLYMERS - Preferred Substrate: The substrate comprises a metal or a polymeric composite material. SPECIFIC COMPOUNDS - The siloxane comprises hexamethyl siloxane.