Study on Reburial Method for The Preservation of Copper Artifacts at The Underwater Archaeological Site

Abstract

To evaluate the corrosion mechanism of copper artifacts and to propose the effective reburial method that suppresses the corrosion of copper artifacts at the underwater archaeological site, corrosion tests were carried out at the Takashima underwater archaeological site using copper and copper with wood. The results of the corrosion test specified that corrosion proceeded by the effect of H₂S or HS^–even in dissolved oxygen （DO）–depleted conditions at the underwater archaeological site. In the case of the copper with wood, the corrosion rate dramatically increased in comparison with the copper samples due to the effects of wood as nutrient salt for sulfate–reducing bacteria. These results indicate that it is necessary to control the mass transfer of chemical species like H₂S, HS^–, and Cu⁺ for suppression of corrosion of copper artifacts at underwater in addition to DO–depleted conditions. The results of the study also suggest that covering copper artifacts using porous media like sandy soil is an effective means for the preservation of them.