Is There an Alternative to Stainless Steel in the Construction Sector?

Building structures are subjected to extreme situations: fluctuating temperatures in summer and winter, precipitation and varying ambient air on the coast, in industrial surroundings or on land. This also applies for façade brackets for rear-ventilated façades (RVF). This successful system not only offers functional safety, but also great creative freedom, as it enables numerous options for cladding façades. As the linking element between bearing wall and building cladding, the substructure of the RVF system is required to bear static loads and must also be able to withstand environmental influences and mechanical stresses – for example from wind. Effective corrosion protection for the profile sheets, anchoring's and fastening elements is therefore essential and can ensure the long-term stability and functionality of the components.

In many cases stainless steel façade brackets are used, thanks to their longevity and great robustness coupled with low maintenance costs and attractive appearance. However, there are also disadvantages to this seemingly simple solution. Fitting or fastening to other steels leads to contact corrosion. This can result in premature loss of functionality. The tensile strength, elasticity and ductility of stainless steel is also often insufficient. Dörken Coatings has therefore looked for an alternative. This resulted in the combination of steel with a coating of zinc flake basecoat and specially-tailored topcoat.

Steel elements coated with zinc flake are often three to five times cheaper than individual stainless steel varieties. At the same time, steel varieties specifically adapted to the function can be utilized. The coating subsequently achieves functionality in addition to longevity. The zinc flake combination has been granted general technical approval by the DIBt – Deutsches Institut für Bautechnik (German Institute for Civil Engineering) and fulfils the requirements of corrosion resistance class C5. Typical environments for this category are areas of near-constant condensation as well as outdoor areas with a coastal atmosphere with a high salt content.

The zinc flake coatings from Dörken Coatings consists of flake-like particles embedded in a binder matrix. This cross-links on the component to generate corrosion protection. An additional topcoat lends the coating further functionalities such as defined coefficient of friction or chemical resistance. The non-destructive fitting of screws and bolts is also enabled. Despite this, the system of base- and topcoat has a coat thickness of just 12–20 μm.

The thin system offers active cathodic protection. In the event of damage to the coating the ignoble zinc in the basecoat sacrifices itself on contact with water and oxygen in favor of the more noble steel base material. This delivers high-performance corrosion protection at a micro layer level. In addition, the surface solution is also suitable for high-tensile steel, as no hydrogen is released in the coating process. The low space requirements for coating units and spray booths mean that zinc flake coatings are often applied in-house or integrated directly into the production line. This enables significant savings to be achieved with regard to pre-treatment and logistics costs, with considerably lower costs also incurred for complaints.