Silver/silver-chloride Reference Electrode
The silver/silver chloride reference electrode is a widely used in the cathodic protection system of sea water applications, performing corrosion potential surveys on boats, yachts and wharfs. This is an extremely useful test and diagnostic tool that should be included within the toolbox of every boat and marine operator.
A silver chloride electrode is a type of reference electrode, commonly used in electrochemical measurements. For example, it is usually the internal reference electrode in pH meters. As another example, the silver chloride electrode is the most commonly used reference electrode for testing cathodic protection corrosion control systems in sea water environments.
The electrode functions as a redox electrode and the reaction is between the silver metal (Ag) and its salt — silver chloride (AgCl, also called silver(I) chloride).
The corresponding equations can be presented as follows:
or an overall reaction can be written:
This reaction is characterized by fast electrode kinetics, meaning that a sufficiently high current can be passed through the electrode with the 100% efficiency of the redox reaction (dissolution of the metal or cathodic deposition of the silver-ions). The reaction has been proven to obey these equations in solutions of pH values between 0 and 13.5.
The Nernst equation below shows the dependence of the potential of the silver-silver(I) chloride electrode on the activity or effective concentration of chloride-ions:
The standard electrode potential E0 against standard hydrogen electrode (SHE) is 0.230V ± 10mV. The potential is however very sensitive to traces of bromide ions which make it more negative. (The more exact standard potential given by an IUPAC review paper is 0.22249 V, with a standard deviation of 0.13 mV at 25 °C.)
l Specifications
Part Number: TJRS
Dimensions:1-1/2" dia. x 6"
Weight:0.4 lbs
Cable length:25 feet
Connector: Banana plug, compatible with handheld digital multimeters
2 Reference Electrode Potentials
| Electrode | Potential E0+Elj | Temperature Coef. |
| (V) at 25 °C | (mV/°C) at around 25 °C | |
| SHE | 0.000 | 0.000 |
| Ag/AgCl/Sat. KCl | +0.197 | -1.01 |
| Ag/AgCl/3.5 mol/kg KCl | +0.205 | -0.73 |
| Ag/AgCl/3.0 mol/kg KCl | +0.210 | |
| Ag/AgCl/1.0 mol/kg KCl | +0.235 | +0.25 |
| Ag/AgCl/0.6 mol/kg KCl | +0.25 |
3. Advantages:
Low cost
Easy to install
Reliable
Rugged
Customized as clients' actual application conditions
4. Features:
Simple construction
Inexpensive to manufacture
Stable potential
Non-toxic components
