Corrosion Monitoring Using Electrochemical Noise Measurements

Abstract The paper describes the use of electrochemical noise, the measurement of potential and current fluctuations, for corrosion monitoring. Also included is the outline of a data management system developed for data logging and analysis of the advanced electrochemical monitoring measurements. The PC based system has been particularly successful in long term corrosion investigations concerned with materials/inhibitor selection and/or the evaluation of those changing process conditions which give rise to localized corrosion, pitting and stress corrosion. The multi-system electrochemical monitoring approach also included the simultaneous logging of electrochemical impedance, and Linear Polarization Resistance Measurement from multi-element probes. The data from various analog instrument modules can be transferred from a Chessell 306 recorder via an interface and a RS-232 link or from digital voltmeters and an IEEE-488M interface. The raw data is stored in a packed format and can be rescaled to provide a suitable graphical and statistical analysis display. This allows periods of specific corrosion activity to be easily recognized and related to changes in the exposure environment or process fluid; also longer term trends can be identified by replotting the data collected over periods of weeks. The total system, monitoring equipment and data management package, has been used to advantage in various laboratory test programs, on-site for atmospheric testing and in-plant for flue gas environments. It is particularly useful in characterizing complex corrosion situations where specific operating periods or changes in environmental conditions give rise to periods of active corrosion, passivity or localized corrosion.