Spectroelectrochemical techniques for the conservation of metallic artefacts

The research presented in this thesis uses laboratory and synchrotron based structural techniques in combination with electrochemistry to test the durability of selected conservation methods. A new piece of portable spectroelectrochemical equipment (the peCell) is also described: the peCell was designed for the long-term monitoring of conservation treatments. Lead carboxylates were selected as the focal point of this research due to the interest in studying their deposition from ethanolic solution and the effectiveness of this type of coating on lead. Therefore the spectroscopic analysis, electrochemical testing in an electrolyte modelling atmospheric corrosion, short-term and longterm volatile organic compound (VOC) exposure, and museum testing of this inhibitor demonstrates an entire package of tests which might be used as a benchmark for testing conservation treatments prior to use on artefacts. In addition the contrasting effects of lead carboxylates in oil paintings and as conservation coatings are discussed. Alongside laboratory spectroelectrochemical data, the corrosion by oak VOCs of a conserved lead sample was studied, (a) using a state-of-the-art in situ timelapse technique on a synchrotron and (b) within a museum environment. Surface analysis by X-ray diffraction (XRD) was used to compare the growth of crystalline surface corrosion products over time: the extent of corrosion can be related to the effectiveness of the various conservation techniques. The peCell is a portable electrochemical or environmental cell which was invented in order to provide a way of tracking the chemical changes occurring in a conserved sample in situ over a long period of time. The cell is capable of holding three samples which can be monitored continuously using open circuit potential and sporadically (i.e. whenever a synchrotron beam line is accessible) using SR-XRD. Other environmental parameters within the cell can also be monitored, such as temperature. The prototype cell was successfully trialled at the XMaS beamline, ESRF using an alternative copper corrosion system

Further advances in lead carboxylate coatings : coating unprimed heritage lead

Further to the previously published work in this journal "Towards a new coating for heritage lead", a coating has been trialled with samples replicating aged lead artefacts. Lead was corroded in an oak environment to simulate storage or display in a wooden case then coated with ethanolic solutions of tetradecanoic and octadecanoic acid. X-ray diffraction and electrochemical impedance data suggests an better-quality coating is formed leading to improved corrosion resistance

Towards a new method for coating heritage lead

Ethanolic solutions of long-chain carboxylic acids can be applied to lead metal substrates to form a coating of lead carboxylate which provides protection against atmospheric pollutants. In this paper we describe the optimal inhibitor concentration for the coating on lead. Electrochemical impedance data taken before and after immersion in media modelling oak emitted volatile organic compounds (VOCs) polluted atmospheres show that coating effectiveness decreases after exposure, but the effect is lessened if longer chain carboxylates are used

Time-lapse synchrotron X-ray diffraction to monitor conservation coatings for heritage lead in atmospheres polluted with oak-emitted volatile organic compounds

We discuss the effectiveness of a lead tetradecanoate coating on lead to protect against harmful volatile organic compounds emitted from oak. The oak volatile organic compounds were characterized by GCMS and the major constituent was found to be acetic acid. Under the test conditions, the coating decreases the rate of corrosion by up to 75% compared to bare lead. The thickness of corrosion products on the sample was also calculated thus demonstrating the power of the time-lapse synchrotron radiation X-ray diffraction technique to deliver a quantitative estimate of the effectiveness of the coating

Tracking the progression of bronze disease – a synchrotron X-ray diffraction study of nantokite hydrolysis

Aims: Increases to radiotherapy dose are constrained by normal tissue effects. The relationship between bowel dose volume data and late bowel toxicity in patients with muscle-invasive bladder cancer treated with radical radiotherapy was assessed. Materials and methods: The bowel was contoured retrospectively on radiotherapy plans of 47 patients recruited to the BC2001 trial (CRUK/01/004). The relationship between bowel volume at various dose levels and prospectively collected late bowel toxicity was explored. Results: Fifteen per cent and 6% of patients experienced grade 1 and grade 2 or more late bowel toxicity, respectively. The mean bowel volume was significantly less at doses 50 Gy in those treated with reduced high dose volume radiotherapy compared with standard radiotherapy. The probability of late bowel toxicity increased as bowel volume increased (P 0.05 for dose levels 30e50 Gy). No grade 2 or more late bowel toxicity was observed in patients with bowel volumes under the thresholds given in the model that predict for 25% probability of late bowel toxicity. Conclusions: There is a dose volume effect for late bowel toxicity in radical bladder radiotherapy. We have modelled the probability of late bowel toxicity from absolute bowel volumes to guide clinicians in assessing radical bladder radiotherapy plans. Thresholds predicting for a 25% probability of late bowel toxicity are proposed as dose volume constraints