surface area of the catalytic components under process conditions without becoming volatile or detrimental to the catalytic species the pgm or other catalytic components can then be applied in a second impregnation step over the cured washcoat layer or can be added directly to the slurry of the washcoat particles and adsorbed thereon prior to coating of the metallic or ceramic substrate forms in a single coating step the washcoat components may also comprise hydroxide precursors that cross link during curing to form oligomers characterized by bridging oxygen groups while the cross linking improves adherence to the substrate the washcoat is not directly covalently bonded to the metallic substrate regardless of the specific composition high solids content viscous slurries of washcoat materials are difficult to apply in uniform thickness over small formed openings or open channels that are part of the pre shaped substrate structures when metal supported catalysts are used to catalyze exothermic processes such as combustion hot spots can arise if the washcoat and the catalytic layer supported thereon is not applied uniformly hot spots lead to accelerated failure of substrate materials as well as to deactivation of the catalytic components thus uniform coating of substrate structures facilitates the production of durable catalytic devices in addition to challenges associated with application of the washcoat layer the constituent materials used to prepare substrates monoliths whether ceramic or.