What is the passive layer of corrosion on the boiler known as?

The passive layer of corrosion on a boiler is known as magnetite. This layer forms primarily from the oxidation of iron in the presence of water and can help protect underlying metal surfaces from further corrosion. Magnetite acts as a barrier, reducing the direct contact of corrosive elements with the metal, thereby prolonging the life of the boiler components.

This layer is essential in boiler operation, as it can stabilize over time and reduce the overall corrosion rate. While rust is a visible corrosion product that occurs when iron oxidizes and combines with moisture, it does not provide the same protective benefits as magnetite. Pitting refers to localized corrosion that occurs in the presence of aggressive agents and can lead to holes in the metal, whereas scale consists of mineral deposits that form when water is heated and contains dissolved substances. These other processes do not serve the same protective function that magnetite does as a passive corrosion layer in maintaining the integrity of boiler materials.