What type of electrolyte solution is commonly used in a close interval potential survey (CIPS) to measure pipeline potentials?

In a close interval potential survey (CIPS), the electrolyte solution commonly used is a saturated copper-copper sulfate (Cu/CuSO4) half-cell. CIPS is a technique used to measure the electrochemical potential of a buried pipeline at close intervals along its length to assess the effectiveness of cathodic protection (CP). The Cu/CuSO4 half-cell serves as a reference electrode. An electrolyte solution is necessary to provide an ionic conductive path between the half-cell and the soil, allowing for accurate potential measurements. The solution allows ions to flow, completing the electrical circuit needed for the measurement. A saturated copper-copper sulfate solution is used because it provides a stable and reproducible reference potential. The solution is prepared by dissolving copper sulfate crystals in distilled water until the solution is saturated, meaning no more crystals can dissolve. A copper rod is then immersed in the saturated solution, creating the half-cell. This half-cell is then placed in contact with the soil above the pipeline, and the potential difference between the pipeline and the half-cell is measured using a high-impedance voltmeter. The measured potential is then used to assess whether the pipeline is adequately protected from corrosion. Other types of reference electrodes and electrolyte solutions can be used in CIPS, but the saturated Cu/CuSO4 half-cell is the most common due to its stability, availability, and ease of use.