What is "sherardising"

n. A form of galvanising in which a metal is heated in the presence of zinc powder which diffuses onto its surface vb. (present participle of sherardise English)

Sherardizing is a process of galvanization of ferrous metal surfaces, also called vapour galvanising and dry galvanizing. The process is named after the British metallurgist Sherard Osborn Cowper-Coles (son of naval inventor Cowper Phipps Coles) who invented and patented the method ca. 1900. This process involves heating the steel parts up to ca. 500°C in a closed rotating drum that also contains metallic zinc dust and possibly an inert filler, such as sand. 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 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 is needed. The process is hydrogen free, therefore a hydrogen embrittlement is excluded.