Abstract
Lead used to be a common material for setting seal to historical documents. Lead seals formed parts of historical documents as a guarantee of their legal validity. Disinfectants are commonly used during the restoration of historical documents. They successfully remove mould, bacteria and microscopic fungi from the surface of parchment documents. However, some disinfectants could also be a source of corrosion damage to lead seals. This work was carried out to examine possible corrosion damage to lead seals caused by disinfectants [a solution of carbethopendecinium bromide, a solution of glutaraldehyde, butanol (vapours), a solution of 1-propanol, 2-propanol + ethanol called Bacillol AF], which are commonly used during restoration of historical documents. The lead corrosion rates were determined by using lead resistometric probes. The solutions of carbethopendecinium bromide and glutaraldehyde increase the lead corrosion rate and corrosion products based on carbonates, nitrates and organic lead salts are formed on the lead surface. The most appropriate disinfectants for the restoration of historical documents with lead seals are alcohol-based solutions, such as butanol (vapours) and a solution of 1-propanol, 2-propanol and ethanol called Bacillol AF.
Highlights
The attaching of seals to documents has been common since ancient times in the area around the Mediterranean Sea [1]
The value of the polarisation resistance describes the corrosion rate of the lead sample after sanding and 30 min exposure in a solution. It follows from the results of measurements of the polarisation resistance that lead has the highest corrosion rates in solutions of 2.5% glutaraldehyde (Rp = 0.7 Ω m2) and 2% carbethopendecinium bromide (Rp = 0.4 Ω m2)
The corrosion resistance was evaluated by resistometric probe measurement
Summary
The attaching of seals to documents has been common since ancient times in the area around the Mediterranean Sea [1]. The mechanism of corrosive attack on lead in a damp atmosphere containing acetic acid is described by the following equation [11]: Pb2+ + 2CH3COOH + 1/2O2 → Pb(CH3COO)2 + H2O (4) It was the purpose of this study to assess the effect of selected disinfectant agents on the corrosion rate of lead using resistometric probes, the polarisation resistance values and the compositions of the corrosion products formed on the surface of the lead following exposure.
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