It is important to control the cooling water of light water reactors （boiling water reactor and pressurized water reactor） to suitable quality in order to reduce corrosion of structural materials and generation of radioactive corrosion products. For that purpose, monitoring of water quality using electrochemical measurement method is necessary. In this article, the application of ECP measurement to BWR is mainly focused, I describe the water quality of light water reactors and the necessity of electrochemical measurement.

Japan society of corrosion engineering has continued the subcommittee activities （the name of the current session: subcommittee of the indoor corrosion） based on the keyword “corrosion of hot dip coated and painted steel sheet in the housing environment” since 1995. Among them, in the laboratory test and the actual housing exposure test, a salt adhesion test was carried out by adhere a certain amount of sea salt in advance to the corrosion in exposure test, and the corrosion rate of the hot dip coated steel sheet and the painted steel sheet were measured by meanings of precise measurement and surface analysis. This paper explained the lifetime evaluation method of these steel sheets used in the structural framework for housing. On the hot dip coated steel sheet, although there is a difference in the corrosion rate in the laboratory test and the simulated test box exposure test and the in-house exposure test, the lifetime of various hot dip coated steel sheets in the house can be predicted with amount the amount of deposited sea salt （Cl^－）. The possibility was shown that for the painted steel sheet, in addition to the blister of coating, the red rust width also be an index that can evaluate the corrosion condition under the residential environment by the reason that the red rust width and the maximum corrosion depth under the paint film are indicating a positive correlation.

In order to investigate the effect of Fe^3＋ on corrosion resistance of 5083 aluminum alloy （A5083） in aqueous solution, electrochemical tests and surface observations were carried out in various solution. Open Circuit Potential （OCP） of the alloy in the solution containing Fe^3＋ shifted to the less-noble direction regardless of the anionic species such as Cl^－ and SO₄^2－. From the polarization curves and the result of surface observation, the effect of Fe^3＋ on the surface of A5083 was suggested that the Fe^3＋ reduction reaction predominantly occurred on compounds.

Anodic reaction around the compounds possibly increased to balance the cathodic reaction. It caused the OCP shifting and the dissolution around compounds.