High-temperature oxidation is a phenomenon where a metal’s surface reacts with oxygen in a high-temperature environment to form an oxide, a process classified as "dry corrosion."
High-temperature oxidation forms an oxide film on the metal's surface. In the case of iron, the iron oxide generated through high-temperature oxidation is also known as "black rust." It forms a black, protective oxide film, such as that on a hot coil or a cast-iron pan, making it an essential factor in the protection and durability of the steel substrate.
The temperature at which high-temperature oxidation occurs on carbon steel is generally considered to be around 570°C (1058°F) or higher, though this varies with composition and operating conditions.
The high-temperature oxidation process generally proceeds in the following steps:
Oxygen molecules are adsorbed onto the metal surface. This typically occurs on a reactive metal surface.
The adsorbed oxygen molecules decompose, and the oxygen atoms diffuse onto the metal surface.
The oxygen atoms react with the metal to form an oxide, which causes the oxide film to grow.
The formed oxide film covers the metal surface, blocking any further supply of oxygen to the metal itself.
While the formed oxide film contributes to metal protection and durability, if it becomes too thick, cracks and peeling can occur. Therefore, it is essential to properly control and manage the high-temperature oxidation surface treatment to extend the lifespan of metal parts and structures.