Kelvin Probe Electrode for Field Detection of Corrosion of Steel in Concrete

While the Kelvin Probe (KP) has been used in a variety of surface scanning applications, the use of the KP in reinforced concrete structures to detect corrosion has been pioneered by previous work performed at the University of South Florida. However, in that work, the scale and construction of the probes was not suited to use in the field. This is primarily attributable to the small operating disk-to-concrete gap which would make the probe unable to accommodate road conditions, such as irregularities in the grading of the road, and local pitting of the surface. Therefore, it was important to investigate whether the KP can be scaled up while still maintaining resolution and fidelity of the measurements taken. The new mobile KP prototype (MKPP) constructed in this work, has a sensing disk that is approximately 10 cm in diameter and is capable of operating up to 2 cm above the concrete surface. Testing consisted of mapping an instrumented test slab simulating a corroding concrete bridge deck, at a rate of travel of about 0.6 mph (~1 ft/s) over the slab surface. The potential map generated through use of the MKPP successfully identified the corroding spot, the location of which was verified using the traditional half-cell potential mapping method outlined in ASTM C 876-09. The MKPP mapping in these trials was approximately 10 times faster than when using the traditional method. The faster potential mapping by the MKPP, while still identifying corroding sites, should allow for more economical and less intrusive survey of the condition of bridge decks. The work set the necessary proof of concept for future demonstration of an array of such probes which would further magnify the beneficial effect