The Effect of Pseudomonas fluorescens on the Corrosion Morphology of Archaeological Tin Bronze Analogues

This work focuses on the localized forms of corrosion caused by microbiological activity, which have seldom been considered for long-term alteration processes of copper-based alloys. To reproduce a seldom-documented corrosion morphology found in some archaeological objects, called ‘tentacle like’, a Pseudomonas fluorescens strain was used on analogues of known composition in a solution containing sulfates, carbonates, nitrates and chlorides. The effect of such bacteria has already been assessed in a previous study, and a localized type of corrosion was defined. The results show that, when a biofilm grows on the surface of the samples, pits are observed under the corrosion products, while in the presence of chloride ions, these pits propagate under the metallic surface and into the matrix, forming uncommon morphologies ascribed to the type “tentacle like”.