Syreoxidationsstal

Syreoxidationsstal is a term used to describe steel that has undergone controlled surface oxidation in an oxygen-containing atmosphere, resulting in an adherent oxide scale on the surface. The concept appears in Swedish metallurgical literature and is used to distinguish steel that has been deliberately oxidized during heat treatment from conventionally finished steel. The oxide layer typically consists of iron oxides such as magnetite (Fe3O4) and hematite (Fe2O3), and may include mixed oxides at alloying element sites.

The oxide layer forms during high-temperature exposure in air or oxygen-rich gas, often in the range of 400–1000°C depending on alloy and desired scale thickness. The thickness can range from a few micrometres to several tens of micrometres. The process is controlled by adjusting temperature, time, atmosphere, and cooling rate. After oxidation, the surface may be subjected to light mechanical finishing or sealing treatments to improve adhesion or appearance.

Properties of syreoxidationsstal include altered surface hardness and wear resistance, and modified corrosion behavior due to the protective or non-protective nature of the oxide scale. A well-adhered, uniform scale can slow further oxidation, but the scale is prone to spallation under mechanical work or thermal cycling and can affect weldability and coating adhesion.

Applications are mainly in surface engineering where a defined oxide layer is desirable for wear resistance, aesthetic patination, or corrosion management. See also oxidation, passivation, weathering steel, and oxide scales.