Weathering steel is a kind of steel that can reduce the corrosion rate by generating a dense protective rust on the steel surface that exerts anti-corrosion performance. Exposure tests of weathering steel with saltwater spraying were performed under three different conditions. When the consistency of sodium chloride solutions was small (0.5% and 1.0%), the effect of rain rinse was observed. However, large consistencies of sodium chloride solutions provided small differences in rust thickness between open air and under roof conditions. From the results of iron transfer resistance measurements, it was observed that protective rust was generated only in a few cases. This result indicated that generation of protective rust was strongly dependent on the corrosive environment. From the results of exposure tests, it became clear that the change of rust thickness with time can be estimated as an exponential function. The constants in the exponential function can be expressed as a function of consistency of sodium chloride solutions.
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