What Should You Be Aware of Before Choosing a Proper Portable Reference Electrode?

Aug 23, 2022

What Should You Be Aware of Before Choosing a Proper Portable Reference Electrode?

In order to determine the performance of the cathodic protection, a monitoring system shall be incorporated. The monitoring system shall incorporate sensors at representative points over the entire structure/anode zone to be protected. The cathodic protection system performance shall be determined by measuring the steel/concrete potential, using reference electrodes.

Below factors should be noted for an appropriate monitoring system
1. Suitable reference electrodes for permanent embedding in concrete include double junction Ag/AgCl/KCl and Mn/MnO2/0,5 M NaOH electrodes.

2. Other sensors, such as potential decay electrodes, current density coupons, macro-cell probes, etc., may also be used in conjunction with reference electrodes.

3. In some environments, such as in the presence of bromides, iodides, or ionizing radiation, Ag/AgCl/KCl electrodes may be unstable. In instances of significant temperature changes, all electrodes will change their electrode potential. In some such circumstances, it may be necessary to utilize potential decay probes only.
Reference electrodes are used to measure absolute potential values, as in 8.6. Their own electrode potential shall be accurate and stable with respect to a standard electrode.

4. This is typically expressed in theory with respect to a standard hydrogen electrode but is more frequently measured in the laboratory with respect to a saturated calomel electrode.
Reference electrodes shall have an electrode potential within ±10 mV of their theoretical value and any batch of reference electrodes shall all have electrode potentials within ±5 mV of their calibration certificates.

Reference electrodes shall be calibrated with respect to a pair of clean and fully maintained laboratory or mapping electrodes in order to demonstrate the above electrode potential accuracy prior to installation. Electrode installation may be improved by precasting electrodes into shrinkage compensated cementitious mortar and ensuring intimate bonding between the mortar and the porous plug of the electrode. All sensors shall be sufficiently robust for installation and permanent exposure in highly alkaline conditions. The cables and cable connections to sensors shall be similarly robust and alkaline resistant and acid resistant if in contact with, or close to, the anode system.

Portable reference electrodes shall be reference electrodes designed to be used either directly on the concrete surface or in conjunction with Lugging probes. Portable reference electrodes to be used directly on the concrete surface shall have an integral, but replaceable, sponge for contact with the concrete. Portable reference electrodes shall be supplied with a calibration certificate and shall be stored, maintained, and handled in full accordance with the manufacturer’s instructions. Portable reference electrodes shall be checked against a known laboratory standard reference electrode, or similar, at the beginning and end of each site application.
What should you be aware of before choosing a proper portable reference electrode:

Note1: Suitable portable reference electrodes include gel-filled, double-junction Ag/AgCl/0,5 M KCl and saturated calomel electrodes (in a non-glass housing) (SCE).
Note2: Calomel electrodes may not be suitable for site use for health and safety reasons as they contain mercury. Cu/saturated CuSO4 electrodes (CSE) are not recommended for use on concrete surfaces due to the high risk of significant errors if copper sulfate leaks onto the concrete surface.