Sherardising or Zinc thermal diffusion is a process of

galvanization Galvanization ( also spelled galvanisation) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are coated by submerging them in a bath of ...

of ferrous metal surfaces, also called vapour galvanising and dry galvanizing. The process is named after British metallurgist Sherard Osborn Cowper-Coles (son of naval inventor Cowper Phipps Coles) who invented and patented the method c. 1900. This process involves heating the steel parts up to 500 °C in a closed rotating drum that contains metallic

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

dust and possibly an inert filler, such as sand.H. G. Arlt, "Finishes on the Metal Parts of Telephone Apparatus", ''Bell Laboratories Record'', Volume 9(4), 175 (December 1932) At temperatures above 300 °C, zinc evaporates and diffuses into the steel substrate forming 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. Part size is limited by 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 is needed. The process is hydrogen-free, hence hydrogen embrittlement is prevented.

Application

During and shortly after

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

, German 5

pfennig The pfennig (; . 'pfennigs' or 'pfennige' ; currency symbol, symbol pf or ₰) or penny is a former Germany, German coin or note, which was an official currency from the 9th century until the introduction of the euro in 2002. While a valua ...

and 10 pfennig coins were sherardised.

Standards

* ISO 17668:2016 (replaced BS EN 13811:2003): Sherardizing. Zinc diffusion coatings on ferrous products. Specification * ISO 14713-3:2017: Zinc coatings. Guidelines and recommendations for the protection against corrosion of iron and steel in structures. Part 3. Sherardizing

References

{{Use dmy dates, date=April 2025 Chemical processes Corrosion prevention Metal plating Zinc sk:Zinkovanie

Application

Standards

See also

References