Sherardising

Sherardizing, Sherard galvanizing or Diffusionsverzinken, a zinc diffusion method to zinc-iron layers to be formed on ferrous workpieces. It is used for corrosion protection. It is named after the developer Sherard Cowper Coles, who invented this method in 1900 in England, he himself has called this process " Vapor galvanizing " ( Dampfverzinken ). Some manufacturers call this method also zinc thermal diffusion, with the thermal diffusion, the Sherardizing nothing to do.

Method

The components to be galvanized, the ( less common ) were freed from interfering impurities previously by blasting or pickling are given with zinc powder and usually an inert filler such as silica sand or corundum in a rotating drum. From 300 ° C evaporating sufficient zinc and diffuses into the metal substrate and forms together with the ferrous surface adhesive zinc -iron alloys. The usual processing temperatures are below 419 ° C, the melting point of zinc. Process temperatures above 419 ° C, see rare use. The layer thickness is up to 80 micrometers.

Benefits

  • Dense, uniform, and highly resistant layers
  • Well suited for complex geometries and cavities
  • Very good adhesion
  • Ideal as a base for colors or rubber coating
  • Suitable for high-strength steels
  • No hydrogen
  • Good temperature resistance
  • Relatively inexpensive

Application

Sherardizing is mainly used for mass production of steel, such as screws, rivets, and clamps. And products produced by sintering or die cutting may be galvanized locking contour with this method. The components to be coated is limited only by the size of the reaction space. Thus, for pipes up to 6m in length, sheet metal parts or large forgings are sherardized. For example, this method was also used in the production of coins in Germany during the First World War and shortly thereafter, are used. This for the following coins:

  • 5 Pfennig, 1915-1922 ( Hunter Catalog No. 297 )
  • 10 Pfennig 1916 to 1922 ( Hunter Catalog No. 298)

Standardize

The Sherardizing is defined in the following European standards:

  • DIN EN 13811: 2003

Sherardizing - Zinc diffusion coatings on ferrous products - Requirements

  • DIN EN ISO 14713-3: 2010

Zinc coatings - Guidelines and recommendations for protection of iron and steel structures against corrosion - Part 3: Sherardizing

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