Catalytic converters, unlike many parts of a car, are not actually required for the car to operate. However, governments around the world have adopted clean air standards that demand that many pollutants produced during the combustion of fuel in automobiles must be converted into less-dangerous forms. The three primary pollutants of concern that are produced by internal combustion engines are hydrocarbons (unburned fuel), carbon monoxide (a poisonous gas), and nitrous oxides (cause acid rain and smog).
The design of most catalytic converters on cars today is very simple. First, the metal housing resembles a muffler in appearance and size. Inside this housing is either a ceramic honeycomb coated with platinum and palladium or hundreds of ceramic beads with the same type of coating. The platinum and palladium are the chemical catalysts that convert the dangerous gases into safer forms, such as the conversion of carbon monoxide into carbon dioxide. However, both platinum and palladium are considered to be precious metals, which is the reason for the high cost of a replacement catalytic converter.
As the engine operates, the three pollutants mentioned earlier move through the exhaust pipe to the catalytic converter. There, the gases are transformed chemically into “safer” forms. The platinum and palladium is not used up in the process, as catalysts only act to speed up a reaction that would have eventually occurred on its own. Most catalytic converters will last for years before needing to be replaced, but once they fail the effects can be felt in the loss of power. Other products being released by the engine may collect on the honeycombs or beads and eventually clog the catalytic converter. With the route for escaping exhaust cut off, the car will lose power and eventually stop operating.
Although expensive, replacement of the catalytic converter is the only option. There is no means by which to repair or refurbish the old converter, though the mechanic will send it in for recycling and re-use of the platinum and palladium. Some car owners may attempt to replace the catalytic converter with a straight pipe within the exhaust system. Sure, the car will run great, but you will be releasing large amounts of pollutants from the engine that are dangerous to humans and wildlife. Many governments have strict laws against such a practice and if you are found to have violated environmental laws you could find yourself in legal trouble. Know your laws and follow them to avoid serious prosecution.