Perforated sheets are simply sheets with punched-out openings. The quality of the thin sheet as the starting material, the perforation process and, in particular, the post-treatment of the perforation patterns are decisive for their durability, as Schäfer Perforated Metal in Neunkirchen explains. This is because the perforation gives the sheets completely different surface properties.
Rounded perforated edges make corrosion protection possible in the first place
When perforating sheet metal, metal punches are pressed into the sheet surface by machine. This creates the specific hole patterns. Break-out burrs occur at the punch exit on the underside of the sheet due to the process. Depending on the application, it is therefore advisable to break the edges after perforating. This procedure ensures that the edges are no longer sharp, but rounded with a defined radius. As a result, the subsequent coating processes run reliably and the corrosion protection lasts for a long time. After mechanical processing, chemical or electrochemical processes are used to apply a protective coating.
A high-quality variant, which is often used in automotive and commercial vehicle production, is cathodic dip coating (CDC). After this step, however, the surface coating is not yet UV-resistant. Another common post-treatment is phosphating. Phosphating is mainly used for components made of steel or iron. Elements made of zinc or other non-ferrous metals can also be phosphated.
Certain processes depend on the base material
Zinc-magnesium is comparatively new as a hot-dip coating of zinc, aluminum and magnesium. Zinc-magnesium-coated flat steels are the starting material for the perforated sheets. At cut edges or scratches, the alloy reacts by forming a solid top layer, which delays the reaction of oxygen and iron.
Other corrosion protection processes depend entirely on the starting material. "For example, anodizing is only possible on aluminium," explains Thomas Schmid, Head of Perforated Metal at Schäfer Werke, in an interview with our editorial team.
You can read a detailed article on the topic of corrosion protection for perforated sheets in the January/February 2025 issue of mo(click here to subscribe) or shortly on oberflaeche.de SI