IN-SITU ELECTROCHEMICAL POTENTIAL MEASUREMENTS IN A DEAERATOR FEEDWATER STORAGE VESSEL

The present paper attempts to describe a study aimed at (a) the 'in si tu' measurement of the electrochemical potential, ECP, of the inner su rfaces of weldments in a working deaerator feedwater storage vessel an d (b) observing the influences of real water chemistry and operational conditions on the electrochemical response. It was established that t he ECP values at two locations in a circumferential weldment (a) could be reliably recorded in situ over a period of some 1700 h, (b) exhibi ted excellent agreement (differences were less than 10 mV) and the ECP responses were identical, (c) varied between +260 and -350 mV(she) de pending upon operating conditions, (d) exhibited a hysteresis effect o ver the initial 400 h period after which ECP values attained their low values which were compatible with low dissolved oxygen water, and (e) exhibited a series of positive shifts in ECP which were identified wi th load changes, which were not significantly affected by pH or conduc tivity. The relationship between ECP and dissolved oxygen, DO, levels in deaerator feedwater at low temperature values of around 110 degrees C recorded from the present study exhibited good agreement with other reported low temperature data (100-150 degrees C) from the literature .