Sustainable

Sherardising products is a cost-effective investment because the diffusion galvanised coating offers durable protection against corrosion and wear and tear. The long service life has been proven for decades in lots of industrial applications.

The service life of a number of zinc coatings in a variety of atmospheric environments is described in EN ISO 14713. The expected service life of a sherardised coating of, on average, 35 µm is more than twenty years if used in an urban environment.

Because the circumstances in accelerated corrosion tests do not correspond to the situation in practice, the result of, for example, the salt spray test in accordance with ISO 9227 does not provide any indication of the expected service life of a diffusion galvanised coating.

In this test oxidation will quickly cause the iron part of the zinc-iron alloy coating to turn an orange-brown colour. However, this is not base material corrosion. This oxidation and discolouring can be prevented through the application of chrome-free passivation.

The corrosion resistance can be substantially increased through the application of a top coating to a diffusion galvanised surface. In salt spray tests, these duplex systems produce results of more than 1,000 hours.

The accelerated corrosion test can provide an indication of service life because the zinc layer is protected by the top coating. However, if this top coating is damaged, there will still be no sub-corrosion because the base material is protected by the underlying zinc layer.