Diagram: Chemical process inside a catalytic converter

Diagram: Chemical process
inside a catalytic converter Maximize

Diagram: Thermal deactivation

Diagram: Thermal
deactivation Maximize

Catalytic converter damage analysis.
Enhanced competence.

General wear and tear on injection systems, ignition system defects, faulty lambda control, but also inadequate maintenance can lead to damage which impacts the catalytic converter. But the cause is often mistakenly taken to be a defective catalytic converter.

Thermal deactivation

Incompletely burned fuel can cause overheating of the active surface and result in thermal deactivation of the catalytic converter. Depending on temperature, possible consequences are: sintering of the noble metals, peeling of the washcoat, or structural changes to the substrate material (the ceramic may even melt).

Apart from the typical ageing that takes place at high temperatures, the loss of catalytic converter efficiency due to poisoning has major importance. Several components of the engine exhaust can impair catalytic activity.

In the past, for example, lead added to the fuel caused irreversible damage to the catalytic converter within a short time. Today it is oxides of sulphur and motor oil constituents like sulphides and sulphates that do damage.

In diesel oxidation catalytic converters an additional problem occurs due to soot particles. In the low exhaust-gas temperature range these particulates are deposited on the washcoat, clogging the pores and thus reducing the active surface. Though this effect can be reversed by raising the exhaust gas temperature, exceptional quantities of soot still can cause thermal damage.

High oil consumption also is a possible cause of catalytic converter deactivation.

Mechanical damage

Mechanical damage occurs usually due to grounding of the catalytic converter bottom during vehicle operation. The cause should be sought in a particular driving style rather than in technical basics. A synchronised canning process rules out ceramic monolith breakage in normal operation.

Mechanical damage - Example 1
Mechanical damage - Example 2
Mechanical damage - Example 3