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optimum protection for valve and medium

The basis for perfect enamelling to the DIN 51178 standard is the correct metallic substrate. ERHARD makes its valves from high-quality spheroidal graphite cast iron, which contains precisely defined fractions of carbon, silicon, manganese, phosphorus, sulphur, magnesium, aluminium and other trace elements. Perfect bonding during firing only occurs with this exact mixture.

ERHARD Pro-Enamel – more than just a coating

With enamelling, the vitreous enamel does not lie on the component as a separate layer, as is the case with powder or wet paints, instead it physically and chemically bonds with the base material. Thanks to the diffusion processes that occur during the firing, excellent adhesion and at the same time a true composite material is created. This is reliably protected against possible tunnelling, even if the valve is mechanically damaged. The composite steel-enamel is absolutely impervious to water vapour and oxygen, diffusion or blistering between the substrate and coating is excluded.

While small cracks can propagate in ordinary enamel, the fibres in ERHARD Pro-Enamel immediately stop cracking. The vitreous enamel forms a keyed connection with the cast iron and forms a bonding or adhesion zone (2) between the enamel layer (1) and the cast iron as substrate material (3), in which the iron and enamel chemically and phisically bond.

This bonding remains stable, even if the material is bent and other stresses such as internal pressure, pipe forces or earth loads, and reliably prevents the enamel from flaking off. ERHARD Pro-Enamel is also highly elastic, similar to glass, as seen in glass fibres or multi-layered car windscreens. A decisive factor here is also for the optimum layer thickness to be selected for the required area of use.

As a special characteristic, ERHARD valves are coated with special fibrous enamel. In this case, short fibres are added to the frit, which prevent the material from tearing if damaged by external forces. A crack cannot continue, instead it is immediately and reliably stopped at the next fibre – similar to a glue, which is used to stop a ladder in tights. Thanks to the fibrous enamel, ERHARD valves with Pro-Enamel have unrivalled impact resistance.


  • ERHARD GmbH & Co. KG
  • Meeboldstraße 22
  • 89522 Heidenheim, Germany