Black finishing according to DIN 50938 or your standards

Unsere Technik: Brünieren


The process of black finishing creates even, black surfaces on ferrous components.

Black finishing is considered a ‘wet’ chemical process. By dipping parts into a hot alkaline oxide solution the surface receives a thin mixed iron-oxide layer consisting of Fe3O4 and FeO. This conversion coating creates a dark black surface on the parts treated. As the surface is merely converted, black finishing is not considered a layering process.



  • optimum dimensional stability by converting surface instead of applying coats
  • protection against corrosion (temporarily together with anti-corrosives)
  • increased wearing resistance of material (flexional/abrasion resistance)
  • conductibility
  • amorphous layering
  • no change of surface structure
  • no distortion
  • temperature resistant up to 300°C

Examples of application

Unsere Technik: Brünieren - Werkstoffe


  • iron
  • steel
  • cast iron
Unsere Technik: Brünieren - Anwendungsgebiete

Areas of application:

  • mechanical engineering
  • tool manufacture
  • roller bearing industry
  • arms technology
Unsere Technik: Brünieren - Weitere Vorteile

Other advantages:

  • inexpensive
  • simple process
  • environmentally friendly
  • special measurements


  • Layer thickness: 0.5 – 2.0 µ
  • Bath size: 2,500 x 1,200 x 700 mm*
  • color: reddish-brown to black
  • up to 2 tons weight per part
  • rack working
  • drum working
* larger parts by turnaround, rings with outside diameter of 2.200 mm by rotating tool

Standard applied::

  • DIN 50938-Fe//[Processes]/[Aftertreatment]


    • Processes available
    • A – One-dip (ca. 4.5 g/m²)

    • B – Two-dip (ca. 5.5 g/m²)
    • Aftertreatment available:
    • T 1 - Coating

    • T4 – oiling, greasing

    • T10 – water displacement agent
  • Your standard


The statement ‘surface acc. to DIN 50938-Fe//B/T4’ means: Treating follows two-dip process with subsequent preservation by dipping into an water-in-oil emulsion.