Sherardising

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Sherardising or sherardizing is a method of galvanising also called vapour galvanising or dry galvanizing. It was named after Sherard Cowper-Coles, who invented and patented the process around 1900.[1][2][3][4] The process is carried by placing goods and zinc powder mainly with an inert filler, such as sand in closed rotating drums. At temperatures above 300°C, Zinc evaporates and diffuses into the steel substrate forming a diffusion bonded Zn-Fe-phases. Any steel grade can be sherardized.

Sherardising is ideal for small parts and parts that require coating of inner surfaces, such as batches of small items. Part size is only limited by the drum size. It is reported that pipes up to 6 m in length for the oil industry are sherardised. If the metal surface is free of scale or oxides, no pretreatment or chemicals are needed. The process is hydrogen free, therefore a hydrogen embitterment is excluded.

Application[edit]

During and shortly after World War I, German 5 Pfennig and 10 Pfennig coins were sherardised.

Standard[edit]

BS EN 13811: 2003 Sherardizing. Zinc diffusion coatings on ferrous products. Specification

BS EN ISO 14713-3: 2009 Zinc coatings. Guidelines and recommendations for the protection against corrosion of iron and steel in structures. Part 3. Sherardizing


See also[edit]

References[edit]

  1. ^ US patent 701298, "Process of depositing metals on metallic surfaces and the product thereof", published 1902/6/3 
  2. ^ "Original Patent (Google patents)". 
  3. ^ Porter, Frank C. (1991). Zinc Handbook. CRC Press. ISBN 978-0-8247-8340-2. 
  4. ^ Eric J. Mittemeijer; Marcel A. J. Somers; F. Natrup; W. Graf (21 November 2014). "20 - Sherardizing: corrosion protection of steels by zinc diffusion coatings". Thermochemical Surface Engineering of Steels: Improving Materials Performance. Elsevier Science. pp. 737–. ISBN 978-0-85709-652-4.