Abstract Theoretically, it is possible to use a measure of voltage difference (ΔE) between an iron electrode and a second electrode to follow the concentration of iron in chemical cleaning solutions, as predicted by the following equation: ΔE=A+Blog[Fe]where A and B are characteristics of the cleaning solvent. Field evaluations of this theory were performed during three superheater/reheater cleanings. In these cleanings, a set of probes was used to continuously monitor the voltage difference between a platinum electrode and a carbon steel electrode. The voltage difference between these probes reflected the amount of iron in the chemical cleaning solutions. Plots of these data were made to verify the equation. A second set of electrochemical corrosion probes was placed in each system to monitor corrosion during the cleanings. Measurements of the corrosion rate followed the trends expected during a normal chemical cleaning and demonstrated that this technique can be applied in a field chemical cleaning. The results of the trials reported in this paper demonstrate that electrochemical monitoring devices can be used for "real-time" monitoring in organic acid chemical cleanings. As the backlog of data is broadened on these systems and their dependability proven, they can become increasingly useful on-line monitoring tools during a chemical cleaning operation.