Flame cleaning of historic wrought iron: practitioner methods and their impact on oxide morphologies and post-treatment corrosion rates

Emmerson, Nicola ORCID: https://orcid.org/0000-0001-5277-0865, Watkinson, David ORCID: https://orcid.org/0000-0002-5696-9780 and Thunberg, Johanna 2019. Flame cleaning of historic wrought iron: practitioner methods and their impact on oxide morphologies and post-treatment corrosion rates. Presented at: Metal 2019: Interim Meeting of the ICOM-CC Metals Working Group, Neuchatel, Switzerland, 2-6 September 2019.

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Abstract

Flame cleaning followed by wire brushing is a common treatment for wrought iron; the flame combusts existing coatings and spalls oxides while wire brushing removes any debris, producing a sound surface for recoating. Although frequently applied, little is known about the effects of the treatment on the substrate material and its post-treatment corrosion rate. This study reports scanning electron microscope backscattered electron imaging (SEM-BEI) and oxygen consumption corrosion rate testing of wrought iron flame cleaned by three practitioners. Wrought iron samples treated by two practitioners corrode up to 4 times faster than uncleaned control samples. Samples cleaned by one practitioner exhibit no increase in corrosion rate. Torch fuel type and temperature attained by the iron are identified as parameters potentially contributing to differences in corrosion rates. Comparing oxide morphology of treated and untreated samples reveals extensive cracking and fragmentation following flame cleaning. This offers multiple pathways for ingress of oxygen and water to the metal core to support corrosion. This data simultaneously calls into question the ethics of flame cleaning and offers evidence that a ‘safe’ method exists, prompting further research into this popular treatment.

Item Type:	Conference or Workshop Item (Paper)
Date Type:	Completion
Status:	Unpublished
Schools:	History, Archaeology and Religion
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	14 February 2019
Last Modified:	25 Oct 2022 13:18
URI:	https://orca.cardiff.ac.uk/id/eprint/119465

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