Cathodic protection system reference electrodes and monitoring sensors
Updated: Jul 17, 2022
The most common method for assessing the performance of an impressed current cathodic protection system is with the use of reference electrodes embedded in the concrete. The reference electrodes are installed in the tidal, splash and atmospheric sections of a concrete structure, and in water for the immersed sections of a concrete structure.
For the immersed sections of a concrete structure such as piles, the commonly used reference electrodes are Zinc and Silver/Silver Chloride reference electrodes which are usually installed in the water in the vicinity of the protected elements. For the atmospheric sections of a concrete structure such as pile caps, piles, headstocks...etc, there are two common types of reference electrodes for embedment in concrete: true half-cell and inert reference electrodes:
• The true half-cell reference electrodes most used in Australia are Silver/Silver Chloride reference electrodes and Manganese Oxide reference electrodes.
• The most common inert reference electrodes in concrete are Titanium reference electrodes.
Irrespective of the type of embedded reference electrode used in concrete for monitoring, to obtain accurate readings, it is essential that the interface area between the electrolytic contact of the reference electrode is in full contact with the surrounding mortar. It is also important that the size of the porous plug for a true reference electrode (or the exposed part of an inert reference electrode) is maximised.
For the mortar surrounding the reference electrode, using mortar which is dosed with chloride to replicate the resistance of concrete may provide more accurate data rather than using a clean mortar. Some manufacturers of Silver/Silver Chloride reference electrodes incorporate with each reference electrode package a dosage of salt for adding to the surrounding mortar.