Microbial-Driven Stabilisation of Archaeological Iron Artefacts

The instability of iron artefacts is rooted in salt contamination during burial and damages associated with exposure to alternative oxygen levels and high relative humidity once excavated. While a combination of chemical and mechanical treatments is utilised to remove the harmful ions (chlorides, sulphur species) and excess bulky corrosion products, these methods can be hazardous for conservation staff’s health, have limited success, or require extensive treatment times. Bio-based treatments provide a potentially greener alternative for removing damaging corrosion and creating biogenic mineral passivation layers, thus remediating concerns over costs, duration, and health and safety. Pseudomonas putida mt-2 (KT2440) is capable of utilising iron under certain conditions and for phosphating mild steel; however, applications have not been made in the cultural heritage sector. To address the potential of using bacteria for conservation purposes, Pseudomonas was assessed for both the bioremediation of salt contaminates and the production of a passivation layer suitable for iron artefacts, with specific conservation concerns in mind. Key factors for optimisation include the role of agitation, chloride content, and oxygen content on bacterial growth and biomineralisation. The initial results indicate a growth preference, not reliance, for NaCl and agitation with partial success of bioconversion of a mineral source.

Experience of Ultrasonic Use to Stabilize Archaeological Iron Artifacts with Active Corrosion

Of all the complex problems of museum storage of archaeological objects, iron objects represent one of the most difficult. In the process of corrosion, an iron object passes through several stages, from oxidation of the metal surface to full mineralization. The greatest problem consists of the items in the stages of oxidation, when the metal is almost completely corroded and converted into minerals. Mineral peels exfoliate under the influence of active corrosion, leading to a loss of historical significance of the object. In the world’s practice of archaeological iron conservation, there are several different ways of stabilization, but none of them can guarantee the integrity of the iron artifact during its museum storage. To date, the most effective conservation method of stabilizing archaeological iron is alkaline sulfite treatment. However, this method has a number of drawbacks, the main of which is the duration of the stabilizing treatment. The authors consider the possibility of increasing the efficiency of the method of processing archaeological iron objects in an alkaline sulfite solution by means of ultrasonic solution activation. In the course of the experimental study, it has been established that the use of ultrasonic in alkaline sulfite treatment hugely increases the efficiency of the method.