Kutsi Akcicek, Jiaxu Zuo, Heather Viles, and Sinan Acikgoz

Department of Engineering Science, University of Oxford, Oxford, UK; School of Geography and the Environment, University of Oxford, Oxford, UK

ABSTRACT

Wrought irons from the 14th (Salisbury Cathedral), 18th (Blenheim Palace), and 20th (Topp & Co., recently re-rolled) centuries are subjected to tensile testing. Failures are investigated using acoustic emission (AE) data, digital image correlation (DIC) strain measurements, post-mortem scanning electron microscopy (SEM), and micro-computed tomography (micro-CT). Analysis of the AE results using principal component analysis and DBSCAN clustering identified three major failure mechanisms, differentiated by the signal’s peak frequency. By analysing the datasets comparatively, three mechanisms are identified and attributed to specific frequency ranges: plastic deformation (35–87 kHz), debonding (125–156 kHz), and fracture (197–298 kHz). The modern specimens exhibited ductile failure, with post-yield behaviour characterised by plastic deformations. In contrast, the historical irons exhibited defect-driven failure, characterised by local strain concentrations dominated by debonding and fracture events. Visual inspections and micro-CT segmentation analyses demonstrated that the failure events were due to the presence of transverse slags, oxide products, and voids. The influence of these defects is systematically evaluated to provide new insight into how macro-mechanical properties are influenced by micro-mechanical failure mechanisms in three different wrought irons.

Download PDF

In-situ acoustic emission monitoring of accelerated corrosion of wrought irons

Kutsi Akcicek 1) , Sinan Acikgoz 1) and Heather Viles 2)

1) Department of Engineering Science, University of Oxford, Oxford, United Kingdom 2) School of Geography and the Environment, University of Oxford, Oxford, United Kingdom

ABSTRACT

Wrought iron bars, with attached waterproofed acoustic emission (AE) sensors, were subject to accelerated degradation in a corrosion chamber. During the transition from the wet to dry stages of the sample, a significant rise in AE hits was observed. Conversely, in fully dry or wet stages, fewer AE hits were detected. Based on the AE activity between transition stages, the results support existing theories of atmospheric corrosion of iron and the significance of wet to dry cycles in this process. Waterproofing of sensors for in-situ corrosion studies has also shown to be viable without causing damage to the sensor itself.

Download PDF from Oxford’s website

Student ‘Metals’ Essay Prize winner 2023

We awarded Alexandra Dziegiel a prize for this impressive essay on historic iron, its deterioration and conservation.

Metals Essay Prize 2023 (.pdf)

Patrick Baty delivered this presentation at our seminar on ‘Colour and Finish’ in London on 15th November 2018

Architectural Ironwork - Coatings & Colour by Patrick Baty (.pdf)

Nicola Emmerson has co-published a scientific paper on corrosion rates of various wrought iron samples when coated with 5 different preparations.

We cannot publish anything but the abstract, but she has made her email address available and if you want to question her about her findings, you can. Please contact us for more information.

The abstract, which raises some of the issues NHIG was founded to solve, is below:

Reference
Emmerson, N. J. and Watkinson, D. E. 2016. Surface preparation of historic wrought iron: evidencing the requirement for standardisation Materials and Corrosion 67 (2), 176 – 189

Abstract
The conservation of heritage wrought iron relies on corrosion prevention by preparation of surfaces and application of protective coatings. In contrast to industrial and engineering treatment of modern steel, conservation practice is not regulated by accepted national and international standards or underpinned by empirical evidence. This paper presents the results of oxygen consumption rate testing (as proxy corrosion rate) of historic wrought iron samples prepared by five commonly applied surface preparation methods and subjected to high humidity environments, with outcomes assessed by use of international standards employed in industrial contexts. Results indicate that choice of surface preparation method has a direct influence on corrosion rate of the uncoated wrought iron, which impacts on performance of the protective coatings that may ultimately determine survival or loss of our rich wrought iron heritage. By implication, more extensive empirical evidence is required to underpin and develop heritage standards for treatment of wrought iron which encompass specifics of the historic material, heritage context and the ethics of conservation practice. The introduction of such standards is called for in order to bring treatment of historic ironwork in line with highly regulated engineering and industrial practices.

Reference

Emmerson, N. J. and Watkinson, D. E. 2016. Surface preparation of historic wrought iron: evidencing the requirement for standardisation Materials and Corrosion 67 (2), 176 – 189

Abstract

The conservation of heritage wrought iron relies on corrosion prevention by preparation of surfaces and application of protective coatings. In contrast to industrial and engineering treatment of modern steel, conservation practice is not regulated by accepted national and international standards or underpinned by empirical evidence. This paper presents the results of oxygen consumption rate testing (as proxy corrosion rate) of historic wrought iron samples prepared by five commonly applied surface preparation methods and subjected to high humidity environments, with outcomes assessed by use of international standards employed in industrial contexts. Results indicate that choice of surface preparation method has a direct influence on corrosion rate of the uncoated wrought iron, which impacts on performance of the protective coatings that may ultimately determine survival or loss of our rich wrought iron heritage. By implication, more extensive empirical evidence is required to underpin and develop heritage standards for treatment of wrought iron which encompass specifics of the historic material, heritage context and the ethics of conservation practice. The introduction of such standards is called for in order to bring treatment of historic ironwork in line with highly regulated engineering and industrial practices.

Keywords

coatings; corrosion; heritage; iron; protection; standards; surface preparation

For a copy of the paper please email Nicola Emmerson
EmmersonNJ@Cardiff.ac.uk

 by Kendra Wilson

Are railings always black?

Before the middle of the 20th century, ironwork was not black. It was much more likely to be green, gray, or red-brown.

Gardenista has a very interesting article on the development of paint colours used on ironwork that dispels the popular myth that Queen Victoria is responsible for all the black ironwork we see today.

Author: H.J. Louw

The Rise of the Metal Window during the Early Industrial Period in Britain, c.1750-1830
UniversityOfCambridge_article3.pdf (26.56 MB)

From the University of Cambridge – Department of Architecture’s downloadable archive of the Journal of Construction History (CHS).

By Matthew Boultwood and Jo Adkins

Lead and You
Lead_and_You-generalversion-16-Jul-2013.pdf (1.08 MB)

By Patrick Baty

The Use of Colour on Architectural Ironwork
TheUseOfColourOnArchitectualIronwork_by_PatrickBaty.pdf - Version 1 (47.67 KB)

By Quentin Collette, Ine Wouters, Corentin De Favereau, Arnaud Peters

Development of riveting technology through an analysis of Belgian patents (1830-1940)
Quentin_Collette_SAHC2012_051.pdf (804.15 KB)