We can give the applied coating various properties or design our galvanizing process in various ways. This all affects the properties of the surface and the product.
At SHERART we process the surface of a product or system in such a way that after treatment it will behave according to the predefined wishes and requirements of the customer. Think of protection against corrosion, but also of shape retention.
Sherardized products have a matte gray appearance, which is often seen as an advantage.
Sherardising is a sustainable solution, because products last longer due to the diffusion galvanizing process. The service life is extended. In addition, it is an environmentally friendly solution. No chemical treatment is required and there is therefore no chemical waste. Because sherardizing is a so-called closed zinc process, no toxic zinc fumes are released.
It’s not necessary to pre-treat the products. Products that are metallic blank can be countersunk without prior application. Contamination does not have to be a problem either, it is removed beforehand by means of jet blasting, after which the sherardization process can start.
Sherardization can be applied to many steel products, systems and shapes. There is even so much that you could say that almost nothing is impossible.
Sherardizing is a reliable and time-honored application, which was already developed in the 1900s. Since that time, the technology has been further refined and improved. The name sherardizing refers to the developer of the technique: Sherard Cowpler-Coles.
In enclosed rotating drums the metal products are heated together with zinc powder. The temperature rises to a temperature between 300 C and 500 ºC. Under these high temperatures, the zinc powder transforms into zinc vapour. This vapor reacts with the product and an even zinc layer is created. Watch out video.
In diffusion galvanizing, or sherardizing, steel or metal is protected by heating it with a zinc powder. The zinc combines with the base material by diffusion. This creates a protective layer that prevents corrosion.
The stable zinc-iron alloys are inextricably linked to the base material. This allows sherardised products to be used at high operating temperatures without diffusion of zinc into the steel. This excludes liquid metal embrittlement.
In contrast to other zinc-based coatings, zinc-iron alloys are resistant to temperatures in excess of 600°C. In addition, sherardised products are also cold-resistant down to a temperature of -40 C
No, the application can determine the maximum or minimum layer thickness.
SHERART’s specialists are happy to advise on this.
Yes. Our accurate process monitoring ensures that products receive the same film thickness, even in the case of repeat orders. This is particularly important for products with fits.
The applied layer thickness is adjustable and reproducible from 10 µm to 100 µm.
Diffusion galvanizing (sherardizing) creates a solid alloy with the metal base material. This cannot just come off or peel off.
The hardness of this layer is about 400 HV (41 HRC) and exceeds the hardness of other zinc layers or lacquers. This property makes sherardizing popular in rough or rugged applications where corrosion protection and wear resistance are important.
Yes. Conventional rubberizing of products requires quite a few actions. Sherardising in advance reduces the number of operations and ultimately also saves costs.
Sherardized products have a microcrystalline rough surface. This allows adhesive primer to be applied to a sherardised surface without pretreatment and results in excellent rubber-metal adhesion. The result is a corrosion-protected, reliable and durable rubber-metal connection.
Hydrogen embrittlement is caused by diffusion of atomic hydrogen in the steel. Sherardizing is a dry galvanizing process under high temperatures (+300 degrees Celsius) and the occurrence of hydrogen embrittlement is therefore excluded.
We have to apply a coating to hot-dip galvanised construction work. When measuring the zinc coating thickness, we find very different values. How thick should/must the zinc layer be?
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.