Structure-to-electrolyte potential measurements are the most fundamental process in the field of corrosion control. The purpose of a potential measurement is to obtain a general idea of the ‘health’ of the cathodic protection system. Potential measurements are often referred to as the ‘language’ of corrosion.
Some companies call it taking a read or measuring a key point, but in the end we are all performing the same type of testing. Many of us perform this activity year after year without acknowledging all of the very import factors involved to complete the work effectively. A well-maintained cathodic protection system requires reliable testing in order to verify its status.
This paper discusses the technical aspect of potential measurements along with testing methods and equipment maintenance recommendations. Simple routine maintenance of the multi-meter, test lead wires and reference electrode can ensure productive testing with trustworthy results. The methods and maintenance discussed will cover everything from reference electrode placement during measurement to the proper tools used for rebuilding a reference electrode.
Potential measurements are often referred to as the ‘language’ of corrosion. They are the most fundamental process in the field of corrosion control. The purpose of potential measurements is to obtain a general idea of the ‘health’ of the cathodic protection system.
The unit for potential measurements is the Volt. Voltage is a measure of electromotive force or the amount of energy (work) to move an electric charge, per unit of electric charge. A pipe-to-soil potential is a measure of the voltage (difference in energy) between the pipe (structure) and the electrolyte (environment).
Potential measurements are generally used to evaluate the effectiveness of cathodic protection. They can be used to classify areas of the structure as anodic or cathodic to one another.
A potential measurement in the field of corrosion control can generally be described as a voltage measurement between a reference electrode (Cu/CuSO4 ½ cell) and a structure (pipe or tank). This is considered a full cell potential measurement. One ½ cell potential is between the copper rod of the reference electrode and the earth (constant). The other ½ cell potential is between the structure (pipe) and the earth (variable).
