The required zinc coating thickness is described in the NEN-EN-ISO 1461:2009 – “Hot dip galvanized coatings on iron and steel articles – Specifications and test methods”. (Unless otherwise agreed by the parties concerned).
The layer thickness depends, among other things, on the material thickness and the material composition of the steel products. For example, for material thicknesses of 6 mm and above, a minimum zinc coating thickness of 70 µm applies, with an average value of at least 85 µm. Maximum values are not given. For steel compositions with reactive elements such as Silicon and/or Phosphorus, higher values may be found as a result of continued growth of zinc alloy layers. As a result, the appearance of the zinc layer may also differ (e.g. dull grey instead of shiny silver grey). For the correct method of measurement and required layer thicknesses for other material thicknesses, please refer to the aforementioned standard. Different layer thicknesses apply to centrifugally galvanised components, which are also mentioned in this standard.We would like to refer to NEN 5254:2003 – “The industrial application of organic coatings to hot-dip galvanised or sherardised products (duplex system)”. This standard governs agreements between the client, the galvanisation plant (or sherardisation plant) and the person applying the organic coating. Further, additional quality requirements for the zinc coating, pretreatment and organic coating are described herein.