- For the evaluation of corrosion resistance of steel sheet, exposure tests in a real
environment and accelerated corrosion tests are commonly used. In order to estimate the variations in the
corrosion rate due to the effects of changeable environmental conditions during these tests, a corrosion
monitoring system using the electrical resistance technique was applied. Two kinds of corrosion sensors,
an Fe sensor (250 μm thick) and a Zn sensor (50μm thick), were used. In the accelerated corrosion test
(ISO16539 Method B), the corrosion depth as evaluated by the sensors displayed a good correlation with
that of the exposure test samples. Thus, the variation in the corrosion rate could be evaluated by the
sensors. It was confirmed that the corrosion rate increased during the wet stage and decreased during the
dry stage. In exposure tests in Okinawa and Kawasaki, the variation of the corrosion rate due to the effects
of changeable environmental conditions throughout the year could be evaluated by the sensors. The
corrosion rate in Okinawa as evaluated by the Fe sensor was greater than that found in Kawasaki.
However, the corrosion rate in Okinawa as evaluated by the Zn sensor was almost the same as that in
Kawasaki. The corrosion sensors could clarify the difference in corrosion behavior between Fe and Zn.
Furthermore, the relationship between the corrosion rate and the environmental factors (temperature,
relative humidity, amount of airborne sea salt, etc.) was analyzed.