Which voltage drop is considered uncontrollable?

The voltage drop in the electrolyte is considered uncontrollable because it is influenced by various environmental factors that are beyond direct control during a cathodic protection (CP) measurement. Factors such as temperature fluctuations, variations in soil composition, saturation levels, and the presence of other chemicals can drastically affect the resistivity of the electrolyte. This variability leads to changes in the voltage drop across the electrolyte that can be unpredictable, making it difficult for operators to manage or adjust directly.

In contrast, voltage drops in conductors, at reference electrodes, and across surfaces can be more precisely measured and controlled through design and operational practices within the cathodic protection system. For example, adjustments can be made to the CP system to mitigate issues with conduction and surface voltage drops, but the unpredictable nature of the electrolyte’s characteristics leads to the conclusion that its voltage drop remains uncontrollable during CP assessments.