The potential of underground pipelines and buried installations in soil or immersed in water is measured relative to reference electrodes (half cells). Reference electrodes are divided into three main categories depend on application such as: oil, gas and petrochemical and marine:

•  Copper / Copper sulfate reference electrode (portable & permanent) for using in soils including Cl-
• Zinc / Zinc sulfate reference electrode (portable & permanent) for using in soils including Cl-
•  Silver / Silver chloride reference electrode (portable & permanent) for using in marine environments
•  Zinc Reference electrode for using in marine environment

Copper / copper sulfate reference electrode is suitable for contact with soil and fresh water, while a silver / silver chloride reference electrode is preferred for immersion in saline water. The zinc reference electrode can be used in clean seawater. Electrodes used as sensing electrodes must be designed to be stable over a long period of time.
The used standard for reference electrodes is BS 7361.

Technical Documents

Datasheet sample of Cu/CuSO4 Reference Electrode

Datasheet sample of Zn/ZnSO4 Reference Electrode