Stainless steel is naturally corrosion-resistant, but it is not immune to rust. While it is less prone to rusting than conventional steels, exposure to damaging chemicals, saline, grease, moisture, or heat for extended periods of time can cause corrosion. The likelihood of corrosion depends on the chromium content of the stainless steel, with higher chromium content reducing the risk of rust formation.
Stainless steel is divided into two general types, which each have a different atomic structure. In general, ferritic stainless steel is magnetic, while austenitic types like 904L stainless steel are not. While both types of steel are iron alloys, there are critical differences in how their atoms are arranged that affect not just their levels of magnetic attraction but also other characteristics like their weldability.In an austenitic stainless steel, the atoms are arranged in what is known as a face-centered cubic (fcc) lattice. Picture the unit cells as a cube: there are atoms at the centers of each of the cube’s faces and also at each of the eight corners of the cube. This sort of atomic arrangement is most likely to show up when the allow contains carbon, nitrogen, manganese or nickel. Ferritic stainless steels, by contrast, are arranged in what is known as a body-centered (bcc) lattice. Atoms are arranged at each of the eight corners of the cube. Another single atom is located in the center of the cube. Silicon, chromium and molybdenum make a bcc crystal structure most likely.
