A catalytic converter consists of a stainless-steel casing that houses a metallic (metalith) or ceramic (monolith) substrate or core. This substrate has a very large number of fine channels running through it along its entire length (like a honeycomb), which increase the amount of surface area available to support the catalyst, which explains why it is also called a catalyst support. This increased surface area also enhances the catalytic effect of the catalyst. The surface of the substrate is coated with a highly porous "washcoat" (which forms a rough, irregular surface that gives the substrate an even larger surface area) to which precious metals (platinum, palladium and rhodium) are added in suspension.
Last update on 2013-07-05 by Stefen Baetge.