Carbon steel, titanium and copper are thought to be candidate materials for an overpack used for the geological disposal of radioactive wastes. In this paper, electrochemical and corrosion studies on the materials in simulated geological disposal environments are reviewed. Deaerated or aerated, single or mixed solutions of NaCl, Na2SO4 and NaHCO3 and bentonite soaked with these solutions have been used as simulated geological disposal environments. Anodic and cathodic polarization curves, corrosion rates, surface films, general corrosion, pitting, crevice corrosion, hydrogen embrittlement, and stress-corrosion cracking of the materials in the environments have been examined.
The combined addition of Si and Cu is effective in order to improve the stress corrosion cracking（SCC）resistance in hot water environment, and SUS315J1（18Cr-10Ni-1.5Si-1Mo-3Cu）has been developed and put in practical use. But, the preset temperature of equipments for supplying hot water in recent years has tended to become high（near 100℃）. Moreover, the influence of anion-species included in hot water on SCC has not been confirmed yet. The SCC resistance of various stainless steels was examined by the immersion test using spot-welded specimens in 200 mg/L Cl－ solution at 60, 95 and 125℃. The materials used were SUS304, SUS315J1, SUS316 and SUS444 cold-rolled steel. SUS315J1 showed the good SCC resistance compared with SUS304 and SUS316 at a temperature under 95℃. The influence of various anion-species（NO3－, SO42－, CO32－ and HCO3－）on SCC was considered by the immersion test or electrochemical measurement in 200 mgL－1 Cl－ solution. These anion-species that generally act as a corrosion inhibitor performed as accelerator on SCC initiation in addition of a small amount of anions. However, SCC tended not to occur in SUS315J1 in these solutions.
The relation between the corrosion control capability of triazole compounds and the parameter drawn by a semiempirical molecular orbital method（MOPAC7）was analyzed, and the validity of calculation chemistry was verified. The corrosion inhibitory action of triazole compounds to iron was dependent on the ease of carrying out of the polarization of molecular orbital when an electric charge approaches. As for the corrosion inhibitory action of triazole compounds to the zinc, what is easy to receive d →π* electron was good. From these, suitable use of the quantum chemistry parameter showed that the interaction of a corrosion inhibitor and a metal side could be presumed.