Visualizing Dynamic and Localized Corrosion Processes on Cathodically Protected Steel Exposed to Soil with Different Moisture Contents

Probing dynamic and localized electrode processes occurring on steel buried in inhomogeneous soils is a technological challenge. In this work, current mapping obtained with an electrochemically integrated multielectrode array has been used, in conjunction with electrode potential and surface pH monitoring, to address this challenge by enabling the visualization of dynamic localized electrode processes occurring on steel surfaces buried in soil. This has enabled understanding of localized corrosion initiation behavior of steel in soil with different moisture contents under the scenario that cathodic protection (CP) was disrupted. Soil moisture contents was found to influence the initiation of localized corrosion by affecting prior-CP generated surface pH and local hydroxyl depletion rates. The maximum localized corrosion was found to occur at 60% water holding capacity. Electrochemically calculated corrosion damages have been verified by surface profilometry measurements.