The criterion of -850mV is referenced to which electrode?

The criterion of -850mV refers specifically to the measurement taken with respect to the Copper-Sulfate Electrode. This reference electrode is commonly used in cathodic protection systems to measure the potential of buried metallic structures, such as pipelines. When a reading of -850mV is noted, it indicates an adequately protected state, reflecting a level of negative potential necessary to prevent corrosion on the structure being evaluated.

The Copper-Sulfate Electrode is widely accepted due to its stable and well-defined potential in natural soil environments, making it an ideal reference for assessing the effectiveness of cathodic protection systems. This criterion is crucial, as maintaining this potential relative to the Copper-Sulfate Electrode is essential for ensuring that cathodic protection measures are effectively mitigating corrosion risks.