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As a versatile material with many uses, steel is widely used in the construction industry. Special coating measures are required if steel components, connecting elements and large surfaces are to be given long-term protection in the atmosphere, earth or water against corrosion damage, thus increasing longevity. Tailored to the respective designated use, these are defined in DIN EN ISO 12944. Whilst corrosion category C4 is required for industrial fields and coastal areas with moderate salt exposure, offshore areas require the C5-M class.

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Christos Tselebidis
Tel: +49 2330 9134054
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Your contact
Christos Tselebidis
Tel: +49 2330 9134054
Contact

Application segments

Long-lasting, effective protection

Steel and reinforced concrete bridges have to withstand extreme loads. Expansion joints, vibration dampers, post-tensioning systems or structural bearings are constantly exposed to alternating weather conditions and bear enormous loads. In order to reach the targeted duration of use of 40 years and satisfy the corrosion protection requirements defined in DIN EN ISO 12944 the steel components utilised must be provided with effective protection. Common here is the use of hot galvanisation, although new technologies such as zinc flake systems also offer numerous advantages.

Requirements

  • C5 M as per DIN ISO 12944
  • Strict requirements to corrosion resistance (1440 h as per DIN EN ISO 9227)

Solutions

Effective corrosion protection in bridge building is provided by the zinc flake coating developed by Dörken MKS, for example. Approved by the Deutsches Institut für Bautechnik (DIBt) for the C5-M field, the technology can be applied in very thin coats of 8-12 µm at very low annealing temperatures (from 180°C) and without hydrogen brittling – particularly advantageous for high-tensile steels. In combination with a suitable top coat a high degree of cathodic protection and specific functional characteristics such as chemical resistance can be achieved. The zinc flake technology is used in the anchoring of restraint systems and noise protection walls as well as cup spring dampers and post-tensioning systems. Steel components with a large surface area can also be protected against corrosion.

Example components

Cup spring dampers

Cup spring dampers are always used where the aim is to transfer and dampen dynamic loads – for example in the stabilisation of suspension cables for arched bridges. A special corrosion protection is elementary to ensure longevity and functionality.

Post-tensioning systems

Post-tensioning systems are used, amongst other applications, in the transverse prestressing of bridges and pier heads and are used in both the construction of new bridges and the retrofitting of existing bridges. As they are exposed to unusual pressure and weathering conditions, protection against corrosion is especially important.

Concrete screws and anchorings

Connecting elements for the securing of restraint systems, noise protection walls, supplementary reinforcements or shear reinforcements on bridge structures must typically satisfy at least corrosion resistance class C5-I or C5-M – the Dörken MKS zinc flake coating meets these requirements.

Corrosion protection for all purposes

From traffic signs to steel crash barriers and anchorings to noise protection walls and retaining systems for slopes (geotechnical engineering): steel safety-relevant equipment is used everywhere on roads and motorways. As these components require long-term protection against weathering, DIN-12944 stipulates high-quality coating with corrosion protection class C5-M. For example, in the case of screw connections it is necessary to coat the thread in order to enable smooth assembly of the components.

Requirements

  • C5 M as per DIN ISO 12944
  • Strict requirements to corrosion resistance (1440 h as per DIN EN ISO 9227)

Solutions

Zinc flake coating is one practical solution. Even an extremely thin coat – a system typically consists of a base coat and a top coat with a total thickness of 8-12 µm – enables a protective effect of up to 1,000 hours to be achieved against base metal corrosion (red rust) in accordance with DIN EN ISO 9227. In addition, screw connections or fasteners coated with the zinc flake technology are especially smooth and easy to assemble thanks to the low coat thickness. This is particularly important for systems used in road construction. Moreover, the highly environmentally-friendly and resource-saving system developed by Dörken can also be used in the coating of steel components with large surface areas.

Example components

Safety barrier systems

Due to extreme influences such as road salt and moisture safety barriers, fastenings and the asphalt screws for anchoring the barriers need to satisfy the highest corrosion protection class, C5-M.

Fasteners for traffic signs

To rule out corrosion damage from the beginning screw connections and fasteners for traffic signs – i.e. screws, nuts and all steel fasteners – are increasingly coated with long-lasting protection.

Bar anchors

Bar anchors are used to secure rocks and slopes, as well as for back anchoring. Compared to other coating systems, the extremely thin coats enable zinc flake technology to offer the advantage of reworking or recutting nuts or sleeves where necessary. This means less labour input and easier assembly.

Increasing safety and functionality

Back-ventilated rainscreens are some of today’s most successful systems, as in addition to the functional safety provided by the many diverse ways of cladding a facade, they also offer great creative freedom. As the link between the load-bearing wall and building skin, the sub-structure in such a rainscreen system absorbs static loads and also has to withstand the influences of the weather and mechanical stresses, for example caused by wind. For the stability and durability of the facade it is therefore hugely important that the profiles, anchors and fasteners used are protected effectively from corrosion.

Requirements

  • C5 M as per DIN ISO 12944
  • Strict requirements to corrosion resistance (1440 h as per DIN EN ISO 9227)

Solutions

As an alternative to standard stainless steel solutions, it is also possible to use high-strength steels with a zinc flake coating for rainscreen systems’ fasteners and sub-structures. The coating is made up of two components – the basecoat and a topcoat, matched to the basecoat concerned. While the zinc flake basecoat ensures high-quality cathodic corrosion protection, the topcoat enables functional qualities such as mechanical durability to be achieved. The technology can be applied in comparatively thin layers of 8-12 µm with very low annealing temperatures and achieves corrosion protection class C5-M as per DIN EN ISO 12944 – meaning that service lives of well over 15 years are guaranteed. A further advantage of zinc flake coating is that in the process of its application no hydrogen embrittlement occurs. In addition, colour marking of the assembly elements with an appropriate topcoat is also possible.

Example components

Facade screws

All sorts of different façade screws are used to anchor attachments made of metal. If they are coated using zinc flake technology, protective effects of up to corrosion protection class C5-M can be achieved. The minimal layer thickness ensures good screw-fastening properties.

Facade brackets

Rainscreens’ sub-structures and their anchorings within the static construction are of great relevance to safety. The façade brackets therefore get coated for example with zinc flake systems in order to achieve long-term corrosion protection.

Steel profile systems

In the case of post-and-beam construction based on the dry glazing system, profiles made of steel or stainless steel arranged on the inward-facing side take on a load-bearing function. Protecting the fasteners using zinc flake technology contributes to long-term functionality and ensures good screw-fastening properties.

Diverse corrosion protection solutions

Whether in space framework, composite construction or scaffolding, for facade rear tensioning or dry lining profiles in wet areas, components made of metal are used in all sorts of fields of application for stabilising, securing and fixing. Wherever these metal structures come into contact with moisture or are exposed to the effects of the weather, corrosion protection plays an important role. In addition to familiar solutions such as hot-dip galvanising or the use of stainless steel components, for special requirements – for example whenever metric or internal threads (nuts) need to be effectively protected – modern coating technologies lend themselves to this task.

Requirements

  • C5 M as per DIN ISO 12944
  • Strict requirements to corrosion resistance (1440 h as per DIN EN ISO 9227)

Solutions

Whenever it is a matter of providing components and fasteners in metal constructions with long-lasting corrosion protection, Dörken MKS zinc flake systems offer a highly effective alternative. The coating is made up of a zinc flake basecoat and an organic or inorganic topcoat and is applied in very thin layer thicknesses at low annealing temperatures (c. 180°C) and without any hydrogen embrittlement. By virtue of the very low layer thickness (from 8µm), very good screw-fastening properties can be achieved for screws and threads – with consistently high corrosion protection up to class C5M. Last but not least, the very thin coating enables not only long-term protection from corrosion, but particularly in the case of larger components a lasting reduction in weight as well.

Example components

Tensile bar systems

Areas in which tensile bar systems are used include in framework and wind bracing elements of roofs and walls, for wood and steel beam trusses and for the rear-tensioning of glass frontages and the bracing of pedestrian bridges. As safety-relevant components they need to be effectively protected from any corrosive influences – using zinc flake technology, even internal threads can be reliably coated.

Node systems

Node systems made of steel are used for example in intricate roof and facade structures and glass and membrane constructions and serve among other things to safely transfer loads.

Scaffold systems

Fasteners and threaded parts or scaffolding systems are typically hot-dip galvanised, but in the interest of long-lasting and effective corrosion protection also get coated using Dörken MKS zinc flake technology.

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