Craufurd, Henry William

SUBJECT AREA: Metallurgy

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fl. 1830s

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English patentee of the process of coating iron with zinc (galvanized iron).

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Although described as Commander of the Royal Navy, other personal details of Craufurd appear to be little known. His process for coating sheet iron with a protective layer of zinc, conveyed as a communication from abroad, was granted a patent in 1837. The details closely resembled, indeed are believed to have been based upon, those developed and patented in France in 1836 by Sorel, who had worked in collaboration with Ledru. There had been French interest in substituting zinc for tin as a coating for iron from 1742 with work by Malouin. Zinc-coated iron saucepans were produced in Rouen in the 1780s, but the work was later abandoned. Craufurd's patent directed that iron objects should be dipped into molten zinc, protected from volatilization by a layer of sal ammoniac (ammonium chloride, NH4Cl which also served as a flux. The quite misleading term "galvanizing" had already been introduced by Sorel for his process. Later its pro-tective properties were discovered to depend for effectiveness on the formation of a thin layer of zinc-iron alloy between the iron sheet and its zinc coating. Craufurd's patent was infringed in England soon after being granted, and was followed by several improvements, particularly those of Edmund Morewood, collaborating with George Rogers in five patents, of which four referred to methods of corrugation. The resulting production of zinc-coated iron implements, together with corrugated iron sheeting quickly adopted for building purposes, developed into an important industry of the West Midlands, Bristol, London and other parts of Britain.

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Bibliography

1837, British patent no. 7,355 (coating sheet iron with zinc).

Further Reading

H.W.Dickinson, 1943–4, "A study of galvanised and corrugated sheet metal", Transactions of the Newcomen Society 24:27–36 (the best and most concise account).

JD