Recently, the initiation period of the steel corrosion has been indirectly forecasted by chloride ion diffusion in cover concrete. However, when the chloride ion contents were continuously measured, the concrete structure was damaged by sampling some cores.
Based on the above backgrounds, in this study, the system which directly forecasted the corrosion initiation period was constructed by a sacrificial electrode. Especially, the threshold value of the sacrificial electrode itself was confirmed to determine the corrosion initiation period. Here, the sacrificial electrode means “a sacrificial material” and “the Expansion-Ring-System”, which were combined with a dummy steel and a lower-ionization metal. More specifically, when a critical chloride ion permeated an arbitrary position in the cover concrete, the sacrificial electrode could sense the corrosion initiation.
In conclusion, the initiation period of the steel corrosion in the concrete could be directly forecasted by some sacrificial electrodes embedded in different cover depths. Also, when the corrosion current density of the sacrificial material was about 0.1-0.2μA/cm² or more, it was determined that the steel started to corrode.