Reliability of electrochemical noise measurements - part 2: First ECG-COMON guideline for an assessment of electrochemical noise measurement devices

摘要

Pro-active ageing management is becoming more and more important for the economical and safe operation of industrial plants. A key element for a pro-active ageing management approach is to apply in-situ corrosion monitoring. The electrochemical noise (EN) technique is an example of a promising method, especially for monitoring localised corrosion phenomena. Currently, research work on the EN technique is carried out in several labs worldwide for different kind of industrial applications but also for the investigation of corrosion mechanisms. A prerequisite for performing serious research on the EN measurement technique is a careful evaluation of the measuring system. Therefore, testing on well-defined dummy cells should always be a preliminary step to assess the baseline noise of the EN measurement equipment and to ensure data validity. For this purpose a guideline has been developed by the European Cooperative Group on Corrosion Monitoring of Nuclear Materials (ECG-COMON, [1]) as an outcome from round-robin testing on EN (see Part 1). The current guideline describes a simple procedure for the performance and evaluation of EN measurement equipment using dummy cells.For this guideline a series of dummy cells consisting of a "star"-arrangement of resistors is used, rather than an electrochemical cell. This provides a well-defined source impedance and noise level, thereby allowing the testing of the noise level and sensitivity of the measuring instruments. Note that, although the resistors used in the dummy cells will generate thermal noise, it is not expected that it will always be possible to measure this noise, and the primary objective of the experiment is to determine the instrument noise levels. The use of a range of resistor values in the dummy cell permits the assessment of the current and potential noise capabilities of the input amplifiers, which are expected to vary according to the source impedance.