Ferritic stainless steels are Iron-Carbon-Chromium alloys where the Carbon content is lower than in martensitic steels and the Chrome content varies between 11% and 30%; these steels have good mechanical strength and moderate resistance to corrosion which increases with the increase in the Chrome percentage, they are not susceptible to hardening treatment and must necessarily be subjected to annealing; weldability is poor, as the material that is overheated undergoes the enlargement of the crystalline grain.

The possible addition of other elements to the alloy serves to increase certain characteristics such as, for example, resistance to localised corrosion, by adding Molybdenum, or resistance to hot oxidation, by adding Aluminium, or to facilitate machinability, by adding Sulphur.

Ferritic stainless steels are also known by the American nomenclature AISI 400 series, they have a crystalline structure with a body-centred cubic lattice (CCC) which makes them magnetic.