‘ In situ’ electrochemical potential measurements in a deaerator feedwater storage vessel

Abstract

The present paper attempts to describe a study aimed at (a) the ‘ in situ’ measurement of the electrochemical potential, ECP, of the inner surfaces of weldments in a working deaerator feedwater storage vessel and (b) observing the influences of real water chemistry and operational conditions on the electrochemical response. It was established that the ECP values at two locations in a circumferential weldment (a) could be reliably recorded in situ over a period of some 1700 h, (b) exhibited excellent agreement (differences were less than 10 mV) and the ECP responses were identical, (c) varied between +260 and −350mV she depending upon operating conditions, (d) exhibited a hysteresis effect over 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 with load changes, which were not significantly affected by pH or conductivity. The relationship between ECP and dissolved oxygen, DO, levels in deacrator feedwater at low temperature values of around 110°C recorded from the present study exhibited good agreement with other reported low temperature data (100–150°C) from the literature.