Catalytic converter theft

Advice from the AA -

There is much more too!

Demand for precious metals and parts that contain them is rising



Demand for precious metals and parts that contain them is rising

If you run a car you need to be aware of the risk of catalytic converter theft, particularly if your car has large ground clearance. Thieves are targetting catalysts – located in the exhaust system under the vehicle – because of the high value of the precious metals they contain.

In these harder times and with precious metal prices rising steadily, the demand for parts that contain them is rising. As a result, the risk of theft of catalytic converters is on the increase again.

On diesel cars, the diesel oxidation catalyst is often integrated with the Diesel Particulate Filter (DPF) and there is anecdotal evidence that these are being stolen for their scrap value too.

Catalytic converters (CATs) have been fitted in the exhaust of the majority of petrol cars manufactured since 1992 and diesel cars since 2001. By chemical reaction CATs substantially reduce harmful pollutants from the exhaust.

The metal case of the CAT contains a ceramic honeycombed structure providing a massive surface area across which the exhaust gases flow.

Precious metals – platinum, palladium and rhodium – are coated onto this ceramic structure as catalysts (a catalyst modifies and increases the rate of a chemical reaction without being consumed itself) for the reactions that 'clean' the exhaust:

  • Oxidising (adding oxygen) carbon monoxide and unburnt hydrocarbons to form carbon dioxide and water, and
  • Reducing (remove oxygen) from other gases such as oxides of nitrogen.


The start of the credit crunch in 2008 and high prices for precious metals resulted in a noticeable increase in thefts of catalytic converters. Thieves simply cut the catalytic converter from the exhaust pipe of a parked car and sell them on to scrap metal dealers.

Taller vehicles (4x4s) are particularly vulnerable as the converters are more accessible. Because they tend to have larger engines, they contain more of the precious metals too.

The ceramic honeycomb has to undergo a chemical process known as 'carbochlorination' to recover the precious metals it contains – generally abroad in countries such as China, Poland, Canada and Latvia.

Once an unmarked converter has been removed from a vehicle it's quite difficult to match it to that vehicle as there aren't any distinguishing marks.

Reduce risk

To reduce the risk of theft of your car's catalytic converter:

  • Garage your car whenever possible
  • Park in well-lit busy areas
  • Look out for people working under cars
  • If the car's high risk consider marking the metal shell of the converter with a unique mark, so that if it is removed by thieves it will be easier to trace back to your vehicle
  • If you operate a small fleet, consider obstructing acess to vehicles with high ground clearance by parking lower vehicles close by
Secure marking

Secure marking

Marking system

Retainagroup offer a kit consisting of a virtually indestructible sticker, metal marking fluid and a window sticker (to warn thieves that the catalytic converter carries an identification mark).

Each mark contains a seven digit code and a 24 hour telephone number for the International Security Register which stores the code against vehicle details.

A catalyst marking kit can be ordered from or by phoning 01233 333000.