High-performance protection for safety components and the environment

High-performance corrosion protection for safety components and the environment

The joining of the national high-speed rail networks to form an integral European network is one of the key issues of common European transport policy and requires the consistent reworking of EU infrastructure policy. In relation to this, the EU aims to significantly increase its financial investment in trans-European rail connections. The European Commission intends to promote a total of nine main transport corridors, making some 26 billion euros available in the 2014 - 2020 planning period. The aid encompasses transport infrastructure projects on rail, road and on the water. Amongst other items, 15,000 kilometres of high-speed rail routes are to be linked up, with the goal the completion of a European main network by 2030.

The further development of rail-related high-speed transport is as dynamic as the object itself. Speeds of between 300 and 400 km/h are now almost daily occurrences on the fastest trains. Test runs have even come close to the 500 km/h mark. Naturally, extreme speeds such as these can only be achieved and maintained in the long term if safety requirements are satisfied. Only in this way is it possible to avoid catastrophic train crashes caused by material failure.

Safety thanks to good quality is paramount

This not only concerns the rolling stock and the safety equipment, the entire rail system and its components also need to be designed to deal with the stresses that arise. High speeds mean high dynamic stress, and this is a challenge for any rail securing component. In particular, the rail clamps, bolts and nuts (clamping set) used in this field need to be able to withstand these forces and compensate them as elastic components. The failure of these safety-relevant parts, for example through corrosion, can have disastrous consequences.

These components can be coated as protection against corrosion. This coating is required to withstand both mechanical forces and diverse weather influences, high temperatures and chemical impact, for example from alkaline or acidic environmental conditions.

The rail clamps used in the area of the track superstructure need to be able to withstand high dynamic forces, various weather influences, high temperature differences and chemical stresses.

High-performance corrosion protection

With zinc flake systems these components - as well as the bolts and corresponding nuts used to secure the rails - are provided with more than high-performance corrosion protection. Combined with a suitable top coat, further requirements regarding temperature resistance, chemical resistance and defined glide and friction characteristics can also be fulfilled. With an overall layer thickness of 20 µm - depending on the structure of the layer, geometry of the parts and form of application - corrosion durability of > 1,000 hours as per DIN EN ISO 9227 is achieved against red and white rust. And there is one aspect in particular that characterises this coating technology: it uses no chromium(VI), the carcinogenic properties of which have resulted in it being listed as a so-called SVHC substance (Substances of Very High Concern) in the EU Reach regulation (Registration, Evaluation, Authorisation of Chemicals).

Our zinc flake base coat offers cathodic corrosion protection through the sacrificial effect of the zinc. The scale-like arrangement of the flake layers creates a barrier effect that significantly retards the onslaught of corrosive media such as moisture and oxygen in comparison to conventional galvanic corrosion coatings. Another advantage: the risk of hydrogen embrittlement of high-strength components does not exist, as no hydrogen is present in the coating process.

As no hydrogen is present in the application of zinc flake systems there is no risk of brittle fractures, as in the case of this high-tensile bolt.

Flexible systems engineering

The selection of coating technique depends on the respective component. All standard painting techniques can be applied. Dip-spin applications are typically used for small mass-produced parts, whilst heavy, non-pourable parts can be coated using either the spin-coating procedure or via spraying. The latter is also used for geometrically-complicated components. After each coating procedure the material is chemically combined in tunnel furnaces at temperatures of approximately 240°C.

As the developer and manufacturer of zinc flake technology, Dörken MKS-Systeme is not only the technology leader in this field, but also a competent partner in the field of plant engineering.