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The Influence of relative humidity and intrinsic chloride on post-excavation corrosion rates of archaeological wrought iron

Watkinson, David E. ORCID:, Rimmer, Melanie B. and Emmerson, Nicola J. ORCID: 2019. The Influence of relative humidity and intrinsic chloride on post-excavation corrosion rates of archaeological wrought iron. Studies in Conservation 64 (8) , pp. 456-471. 10.1080/00393630.2018.1565006

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This study examined the impact of relative humidity (RH) on the corrosion rate of 129 archaeological iron nails from two sites. Oxygen consumption of individual nails in controlled RH was used as a corrosion rate proxy to deliver quantitative data on corrosion rate as a function of RH. This was negligible at 20% RH, slow up to 40% RH for both sites, and increased rapidly at 60% RH for Roman nails from Caerleon (Wales) and at 70% RH for medieval nails from Billingsgate (London). The nails were digested and their chloride content was determined and related to their oxygen consumption at specific RH values. While a generic pattern of corrosion as a function of chloride was identified, for any single concentration of chloride corrosion rate was not predictable. Desiccation is in common use to control post-excavation corrosion of archaeological iron; quantifying how differing levels of desiccation changed corrosion rate provided a scaled tool for identifying corrosion risk, estimating object longevity, and calculating cost benefit for storage options.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: History, Archaeology and Religion
Additional Information: This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Publisher: Routledge
ISSN: 0039-3630
Date of First Compliant Deposit: 14 February 2019
Date of Acceptance: 29 December 2018
Last Modified: 03 May 2023 01:58

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