Historically corrosion testing, corrosion surveys, and cathodic protection design surveys included soil analysis testing for corrosive soils. Soil testing detects PH, Sulphates, Chlorides, Fe, and various other contaminants, and the results are used to determine the corrosivity of the soil.
They can be of great assistance when choosing the type and location for the proper placement of a reference electrode to determine the adequacy of your cathodic protection system on a specific structure.
Reference electrodes are delicate instruments and should be treated as such. They should be installed in proper soils to lessen contamination and possible failure from contamination. Any soil/electrode issues can be avoided if appropriate corrosion soil analysis practices are followed before selecting and introducing a reference electrode into the system.
In most cases, the reference electrode manufacturer will recommend that in areas where permanent electrodes are to be installed, a simple soil analysis must be performed to determine the proper type of electrode to be used and the proper location.
Contaminant Effects Example
Chloride plus bromide can be deadly to any copper-copper sulfate and zinc-zinc sulfate reference electrodes and ideally used in or underground cathodic protection applications where the salt concentration is minimum or very low.
However, silver-silver chloride reference electrodes are ideally suited for use with seawater applications, where chloride levels range between 1,000 parts per million. At the same time, it is essential to note that Sulfide levels above 100 parts per million will reduce the life of any copper-copper sulfate, silver-silver chloride, and zinc-zinc sulfate reference electrode.
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