Porous ceramic catalyst supports or filters to be provided with catalyst
coatings via oxide washcoating processes are pre-coated with polymer
barrier layers to prevent washcoat nanoparticle intrusion into the
microcracked and/or microporous surfaces of the ceramics, the barrier
coatings being formed of hydrocarbon polymers that are soluble or
dispersible in polar media, capable of forming neutral or hydrophilic
surfaces on porous ceramic supports, and completely vaporizable at
moderate washcoat stabilization or catalyst activation temperatures.