ABSTRACT
Corrosion Domains....................................................................... 518
14.4 Measurement Techniques........................................................................... 520
14.4.1 Electrochemical Cell ...................................................................... 520
14.4.2 Electrochemical Interfaces............................................................. 521
14.4.3 Signal Conditioning....................................................................... 523
14.4.4 Data Acquisition System............................................................... 525
14.4.5 Choice of Parameters and Measured Quantities ........................... 526
14.4.6 Measurement Problems ................................................................. 530
14.5 Data Interpretation .................................................................................... 535
14.5.1 Direct Methods ............................................................................. 535
14.5.2 Indirect Methods ........................................................................... 540
14.5.3 Methods to Detect Localized Corrosion ....................................... 551
14.6 Recent Developments in ENM .................................................................. 552
14.7 Conclusions ................................................................................................ 554
Acknowledgments ................................................................................................ 555
Appendix A .......................................................................................................... 556
Background on Random Signals and Digital Signal Processing ................ 556
Generalities on Random Signals ................................................... 556
Digital Signal Processing ............................................................... 558
Signal Processing for Two Random Signals.................................. 561
Appendix B .......................................................................................................... 562
Noise Analysis of a Conventional VA ....................................................... 562
Appendix C .......................................................................................................... 563
SD of a Linearly Drifting Signal ................................................................ 563
References ............................................................................................................ 564
14.1 INTRODUCTION
Many semimacroscopic phenomena related to corrosion, either localized or uniform,
are stochastic by nature. This often complicates the use of the other in situ electrical
techniques, such as polarization curves, electrochemical impedance spectroscopy
(EIS), etc., which are described in different chapters of this book. Moreover, perturb-
ation signals applied in some deterministic techniques may lead to an alteration of the
process studied. A simple ‘‘listening’’ to the galvanic system through the analysis of the
spontaneous fluctuations of the electrical quantities, current and potential, known as
electrochemical noise (EN), appears as the method of choice for its study, with a
number of attractive features for corrosion research and engineering.
