Iron remains show the corrosion behavior of metal materials over a long term while buried in the soil. The data provide useful information in the study of the stability of overpack (carbon steel) under geological disposal conditions. And they also provide important information for the conservation science of important items of cultural heritage. There are two major microbial influences on the metal material surface : corrosion caused by microbes (microbially influenced corrosion, MIC) ; and mineralization by microbes (biomineralization). To observe these two roles, an iron reducing bacteria was cultured in a liquid medium with carbon steel and detection of corroded products were carried out by XRD method in this study.
Iron reducing bacteria was cultured under static conditions for 41 days with carbon steel. The result showed that a complex (biofilm, bacteria, etc.) was generated by the bacteria and covered the surface of the carbon steel. By using a microscope, the corrosion product was revealed to be formed of green and white crystal, or needle-shaped product and lozenge crystal by SEM observation. The green crystal was vivianite (Fe2+3(PO4)2・8H2O) measuring 50˜250 μm. In a corrosion process of an iron material surface, iron ion Fe2+ is dissolved from the iron in a cathode reaction, and generates Fe3+ oxide as corrosion product. It appears that vivianite can be also generated as corrosion product in an environment rich in Fe2+ and phosphate by activity of an iron reducing bacteria. Some data on the morphological feature of these corrosion products were obtained.