Abstract
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.
