SFS drill-in hinge 3-piece frame C18R blackened

Steel is an iron-carbon alloy with a maximum carbon content of 2% by mass. The steels achieve their intended physical and mechanical properties through various hardening, annealing and tempering processes. It is also possible to harden the edge zone by surface hardening, case hardening or nitriding. Well-known steel grades are structural steels, free-machining steels, case-hardening steels, nitriding steels, tempering steels, tool steels and stainless steels.

Blackening serves to form a thin protective layer on ferrous surfaces in order to reduce corrosion, alter colour and reflectivity, or – in the case of specially adapted processes – improve tribological properties (e.g. for roller bearings). Due to the very thin thickness of the blackened layer and the incomplete passivation of the iron, the level of corrosion protection is very low.