Electrochemical noise (EN) has been intensively investigated for the last few decades. There are practical applications of EN measurements for corrosion recognition but the phenomenon needs still further research. The experimental results of correlation between the surface damages of the metal electrodes and the intensity of voltage fluctuations observed between two nominally identically prepared electrodes are presented. The sets of carbon steel electrodes were applied. Only the metal surfaces were exposed to the electrolyte. The low-frequency voltage noise was continuously registered and the pictures of the electrode surfaces were taken every 30 minutes. The pits, which were created on the metal surface, were detected by Matlab software and compared with the statistical parameters of the observed voltage noise. The acts of the individual pits creation were strictly related to the presence and intensity of transients, characteristic for meta-stable pitting processes in carbon steel.
The experimental setup is described. Some detailed remarks according to the applied detection algorithms of the metal damage are also included.
Nonlinear processes are often encountered in the practice of electrochemical corrosion measurements. Especially, activation controlled processes are inherently nonlinear. In the investigations of electrode reactions linear approximation is common approach. In this introductory paper the possibility of extension of electrochemical noise measurements to the nonlinear regime is presented. The authors focus on the case of cathodic polarization of electrochemical systems what is extremely important for corrosion protection.
Corrosion in concrete can cause disastrous destructions of bridges and other constructions. Different methods of corrosion monitoring can be applied including electrochemical noise despite its disadvantageous limitations. Noise measurements enable continuous monitoring of corrosive conditions inside concrete and recognition when corrosion starts to make trouble there.
Results of electrochemical noise measurements in concrete are presented. Polarization resistance of carbon steel is estimated by current and voltage noise measurements. Changes of factor 2-4 of the estimated polarization resistance are recognized during time of noise registration. The observed changes in uniform corrosion rate can be identified by electrochemical noise analysis. Limitations of the applied method of polarization resistance evaluation are considered and presented.