What is the catalytic converter, and why is it stolen so often?

Why a catalytic converter?

Cars are the scapegoat for ‘air sickness’, even though various studies show that other sources, such as industrial plants, thermal power stations, old heating plants, commercial vehicles and the old public transport in our cities, are more polluting.

Most vehicles are powered by liquid or gaseous fuels derived from oil (petrol, diesel and LPG) and, in increasing proportions, by methane. All these energy sources have in common, except for methane, is their unfortunate tendency to produce, as a result of the chemical reactions that occur during combustion, certain pollutants that are harmful to the health of living beings. In theory, following the perfect combustion of pure fossil fuel, only water vapour (H2O) and carbon dioxide (CO2), the latter responsible for the greenhouse effect, should be produced.

In reality, the combustion that occurs in engines is far from complete, and fuels contain many impurities (e.g. sulphur) and additives, even though in smaller quantities than before(in the past). As a result, pollutants are emitted into the atmosphere that can be grouped, in terms of their regulation, into four families: carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx) and, typical of Diesel engines, particulate matter (PM10).

CO2 is not on the list for two reasons. The first is that it is not toxic, unlike those above. The second reason is that it cannot be reduced. You have to get over it; carbon dioxide is the result of combustion: burning something produces CO2. When all goes well…

Today, the simplest and most easily implemented method to reduce the CO2 emitted is to reforest, to plant trees that absorb the CO2 we produce.

What is the catalytic converter?

Cars face increasingly stringent environmental regulations. The catalytic converter was imposed on petrol cars as early as 1993 and four years later on diesel cars. The particulate filter, meanwhile, made its way onto diesel cars before making its way into the exhaust pipes of petrol cars. But do you really know what this anti-pollution device consists of? How does it work?

The catalytic converter is a device compulsory on all cars on sale, thanks to which the exhaust gases are cleaned mainly of many of the most polluting components that are harmful to human, animal and plant health.

Internally, it can be made in two ways: with many fine metal sheets rolled on top of each other to form many small channels or with a ceramic honeycomb structure.

In both cases, the surfaces in question are coated with three rare and very expensive metals: platinum, palladium and rhodium (the real catalysts).

A catalyst is a substance capable of accelerating a chemical reaction that would take place anyway but at higher temperatures and pressures.

Hence, the catalytic converter, thanks to the three aforementioned metals, transforms pollutants (HC, CO and NOx) into less harmful substances without reaching high temperatures.

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Why do polluting gases form?

They form because, in our engines, we do not have ideal combustion. In the combustion chamber, we have areas where the fuel does not burn completely and other regions where it burns at too high a temperature.

The result is an economic loss and the release of toxic pollutants into the atmosphere.

How long does a catalytic converter last?

A catalytic converter will not fill up or wear out given ideal operating conditions. It should – in theory, last the life of the car.

The effectiveness of the catalytic converter can always be attributed to the efficiency with which the precious active metals it contains. Rhodium, palladium and platinum can trigger the chemical reactions necessary to break down pollutants that would otherwise be released into the atmosphere.

As the number of kilometres travelled increases, the active components of the catalytic converter tend to reduce their effectiveness, both because they are continuously exposed to very high temperatures and because exposure to the chemicals in the exhaust gas eventually changes their surface structure, degrading it. As a result, an increasing proportion of unburned gases, nitrogen oxides and carbon monoxide escape without being inactivated by the catalytic converter.

catalytic converter honeycomb destroyed — This is a completely destroyed honeycomb catalytic converter!

Catalytic converters are designed to function properly for at least 200,000 kilometres. Experts recommend a check from 160,000 kilometres onwards, but the MOT test, with the exhaust gas inspection, also verifies the catalytic converter’s proper functioning.

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The fragility of the catalytic converter

One aspect of paying attention to is the fragility of the catalyst. Although the outer casing is metallic and therefore relatively robust, inside the catalytic converter is, as mentioned, a porous ceramic enriched with metals. The ceramic, being somewhat brittle, breaks easily upon impact with a bumpy surface or pavement edge.

In addition to losing its effectiveness, an internally fractured catalytic converter can lose pieces that end up in the exhaust gas circuit. Ultimately, if the car suffers a bottom bump, it is advisable to have it checked at the workshop to see if the catalytic converter shows signs of possible damage. If so, it is preferable to subject the car to an exhaust-gas test without waiting for the next overhaul.

Why do thieves steal catalytic converters?

The value of the catalytic converter can be over 1,000 pounds for premium models and makes it insertable into the parts trade black market as long as it comes from a car with few kilometres. In addition to this value, what attracts thieves is the presence in this device of rare metals, including platinum, palladium and rhodium. These metals are worth ten times more than gold and can reach astronomical prices per kg, especially since they have become necessary in catalytic converters.

In detail, there are between 6 and 30 grams of rare metals in each catalytic converter, depending on the number (single or twin exhaust) and the engine size.

How to protect the catalytic converter from thieves?

There are many anti-theft devices on the market for catalytic converters, but not all of them can protect these efficiently. The safest are the strong metal shields, plates and cages.

Our team of experts can advise you on the best protection for your car’s catalytic converter.