Corrosion in central heating systems can lead to a build up of sludge which, over time, can cause problems and breakdowns.

The oxygen contained in water can be released as it is heated and this leads to corrosion of steel components.

Rusting is an oxidation reaction.The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust.

Here is the word equation for the reaction:
iron + water + oxygen → hydrated iron(III) oxide (Ferricoxide)
Fe2O3, It is reddish brown in colour - Rust.

The most common symptom of corrosion within a central heating system is sludge, a black, mud like, deposit resulting from the reaction between the water in your system and the steel in the radiators.

The best way to protect your heating system is to clean with powerflush and use a chemical treatment, a magnetic filter.