Effect of heat treatment in reducing plasma environments on chloride ion removal and corrosion of oxidised steel artefacts

Abstract

The application of reducing, low pressure, radio frequency plasma at temperatures in the range 240–400°C for the conservation of iron artefacts has been studied. For this purpose, steel oxidised either in a salt spray cabinet or in the soil, together with excavated objects from a collection from Mount Athos, were treated. Post-corrosion experiments, including electrochemical polarisation studies and exposure in a humid atmosphere, revealed improved behaviour for specimens treated in H₂ plasma diluted with N₂ and CH₄ . Using instrumental neutron activation analysis, measurements were made of the chloride ion removal from the corrosion layer after H₂ plasma treatment. This was found to be a consequence of heating rather than of the plasma treatment.