Second Postgraduate Conservation Research Seminar
Science Museum, London SW7 2DD, UK
8-9 February 1996

THE ATMOSPHERIC CORROSION OF LEAD -- A SURFACE STUDY (ABSTRACT)

Leon Black

Leon.Black@bristol.ac.uk

Interface Analysis Centre, University of Bristol, Oldbury House, 121 St. Michael's Hill, Bristol BS2 8BS, United Kingdom

Lead is used extensively as a roofing material in the United Kingdom, particularly on historic buildings. Upon exposure to the outdoor environment lead develops a grey patina, resulting in the metal's characteristic appearance. This patina may be non-adherent, and so may result in 'run-off' staining of adjacent areas, thus spoiling the aesthetic appeal of a lead roof.

It is a desirable requirement of a lead patina that it be insoluble, stable, and adherent, thereby improving the lifetime and appearance of a roof and adjacent areas. This project seeks to determine the role of various environmental parameters in the formation of a lead patina.

Various surface analytical techniques have been used, but Laser Raman Spectroscopy and X-ray Photoelectron Spectroscopy have proved ideal for the identification of lead compounds, and the subsequent determination of the surface composition. The analysis of field-exposed samples has formed the bulk of the study. The effects of time, environment, alloy composition, and initial date of exposure have been investigated. The interaction of the lead in contact with various woods has also been investigated.

Facilities at the Interface Analysis Centre enable very thin patina films to be analysed. This has enabled the analysis of samples after much shorter periods of exposure than is possible by conventional techniques, providing information on the initial patination processes occuring on the lead surface.

The initial corrosion processes can be simulated under controlled conditions to observe patination on an atomic layer scale. The controlled oxidation of lead has been performed, and it is hoped that future work will examine the effects of other corrosive gases such as SO2 and NOx.

The methods, techniques, and conclusions found in individual papers are the work and responsibility of the author of the paper, and should in no way be thought to represent the opinion or endorsement of either the Journal of Conservation & Museum Studies, the Institute of Archaeology, or University College London. No liability or contract is accepted or implied by the publication of these data.

Copyright © Leon Black, 1996. All rights reserved.
http://www.ucl.ac.uk/archaeology/conservation/jcms/
jcms@ucl.ac.uk