The measurement method of the ACM sensor under the atmospheric corrosion environment was described with actual samples. By analyzing the sensor output and humidity data obtained every 10 minutes, it is possible to estimate the wetting time and sea salt attachment amount, and by correcting the sensor output during rainfall, corrosion rate in the outdoor can be estimated.
Atmospheric corrosion is a complex phenomenon that goes on under thin water film while being affected by various environmental factors. In this paper, the atmospheric corrosion researches using the electrochemical impedance method were described. The impedance characteristics under thin water film, the corrosion monitoring method using electrochemical impedance and the application example, and the corrosion monitoring research in actual outdoor environment were introduced.
Various protective paint systems for steel road bridges have been exposed for 30 years with steel actual-size specimens located off the Suruga coast. From the obtained results, it became clear that the response of electrochemical measurement is correlated roughly with degraded level of the paint systems.
It is important to understand the relation between changeable environmental condition and corrosion behavior of each weathering steel for maintenance management of weathering steel structures. For this subject, it is thought that corrosion monitoring by using the electrical resistance technique is the most suitable. In this study, corrosion behavior in ISO16539 Method B that simulates atmospheric corrosion environment and actual use environment was measured. The difference of corrosion behavior among weathering steels could be clearly measured by the unit μm both in laboratory test and exposure test. However, in only high salinity environment, the output corrosion loss of sensor was larger than actual corrosion loss by increasing the partial electrical resistance caused by large roughness due to locally corrosion on the sensor. And applicable salinity environment for this sensor was decided up to 1 mdd of airborne sea salt. Thus, by using the electrical resistance technique, the difference of corrosion behavior of each weathering steel can be measured, furthermore, it has possibility that environmental condition in which weathering steels show significant corrosion resistance might be clarified by comparing with environmental factors.
To evaluate progress of the rebar corrosion in the RC structure quantitatively, the change with time of corrosion rate of a rebar in concrete is measured by the corrosion rate monitoring using the Tafel extrapolation method and the small size embedded sensor. As a result, using the prediction model of the corrosion rate from result of the measurement, the measurement from the middle of in-service period can estimate corrosion mass loss with around ±20％ of real corrosion mass loss.