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 procees 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 substrat forming a diffusion bonded Zn-Fe-phases.

Sherardising is ideal for small parts and parts that require coating of inner surfaces, such as batches of small items. The original system was quite complicated and expensive; however, today there are new systems in use which are simple, cost effective, and use less or no preparatory chemicals, making them environmentally friendly.

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 (in English). Elsevier Science. pp. 737–. ISBN 978-0-85709-652-4.