Monitoring System NDU for Determination of Corrosion Processes of Reactor Vessels and Piping in Chemical Plants

For monitoring of the corrosion activities within a chemical apparatus different methods are known, as e.g.:

Supervision of immersed specimens at intervals
Measurement of wall potentials and redox - potentials
Determination of the polarisation resistance or the electrode impedance of specimens within the apparatus

Another method has been developed in the past decade, but hitherto its application was restricted to laboratorial use: The evaluation of the electric noise produced by electrochemical processes.

Electric currents produced by electrochemical processes show time - depending fluctuations, commonly called noise. This noise can be measured both as a current signal as well as a potential signal. Besides long - term fluctuations ("drift"), aperiodic oscillations are observed. Their frequency spectrum is determined by the chemical reaction. Theoretical works on these effects were first published by Pisarenko and Tyagai¹. Technical use of this phenomenon could be achieved as soon as appropriate electronic circuits were available which had low intrinsic noise. The noise of different electrode reactions was measured², very sophisticated systems allowed to study the noise of metals in the passive state^{3, 4}.

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