The catalyst in catalytic converters (CATS) is made of platinum, palladium, and/or rhodium. These are all precious metals making CATS expensive The price of these metals is so high that converters are being cut off of trucks right on the street
Two things which can damage a cat are lead and silicon Lead comes from leaded gas which is quite rare nowadays Silicon is present in engine coolant, so if a condition exists in which the coolant is leaking into the exhaust it can poison the CAT. If the vehicle is smoking out the exhaust this could be coolant and the vehicle should not be driven. Another condition which can cause damage to the CAT is an engine misfire which puts unburned fuel into the CAT causing it to overheat and break apart If this happens the converter breaks apart and some pieces often get stuck in the muffler causing a restriction necessitating replacement of the muffler too as long as the vehicle’s onboard diagnostic system is working, a check engine light will flash on and off if this misfire condition is present. A vehicle should never be driven if the check engine light is flashing.