Steel is a material that is alloyed with carbon in iron. Darkening occurs as a result of the formation of a rust layer on the surface of the steel. Rust forms as a result of the reaction of the iron on the surface of the steel with oxygen. In carbon steel, carbon can also accelerate rust formation.
The fundamental reasons for why steel rusts can include:
1. Oxidation: When steel comes into contact with oxygen in the atmosphere, the surface of the iron oxidizes. As a result of this reaction, a layer of iron oxide called rust forms on the surface of the steel. Rust changes the color of the steel and can lead to cracks and corrosion on its surface.
2. Moisture and Water: Moisture and water on the surface of steel can accelerate rust formation. Especially salty water or salt solutions can increase the rate of steel darkening. Steel can rust more quickly in such environments.
3. Pollutants: Air pollution, industrial waste, and chemical substances can accelerate the rusting process on the surface of steel. Such pollutants can disrupt the protective oxide layer on the steel.
4. Carbon Content: The amount of carbon in steel can affect the rate of rusting. Low-carbon steels may be less prone to rusting, while high-carbon steels can darken more quickly.
5. Surface Coatings: Steel products are often protected with coatings to prevent rusting. If these coatings are damaged or worn, the steel surface can rust more easily.
To prevent or delay darkening, steel surfaces should be regularly cleaned, protective coatings should be used, and steel should be kept away from moisture. Additionally, special steel alloys with high rust resistance can be preferred.