Electromagnetic corrosion sensors offer a rapid, non-invasive way to assess rebar condition in concrete retaining walls. This article walks through a field deployment on a 300-meter highway retaining wall, where half-cell potential mapping and linear polarization resistance measurements were combined.
The wall, constructed in the early 2000s, showed visible staining and minor spalling along the lower third of its length. Our team deployed a Gecor 8 corrosion rate meter with a copper-copper sulfate reference electrode. Measurements were taken on a 1.5-meter grid across the entire wall face, totaling 200 survey points.
Results showed active corrosion in the lower third of the wall due to chloride ingress from de-icing salts. Half-cell potentials in that zone ranged from –350 mV to –480 mV vs. CSE, indicating a high probability of active corrosion. Linear polarization resistance measurements confirmed corrosion current densities above 0.5 µA/cm² in the same region.
We discuss sensor calibration, environmental corrections, and how the data informed a cathodic protection design. Temperature and moisture corrections were applied using the on-board thermocouple and a surface moisture sensor. The final report recommended a hybrid galvanic anode system for the lower 1.2 meters of the wall, with a 20-year design life.
The client approved the cathodic protection installation, and follow-up monitoring six months later showed a 70% reduction in corrosion rates. This case demonstrates that electromagnetic corrosion assessment, when combined with proper field protocols, provides actionable data for extending the service life of reinforced concrete retaining walls.