Electrochemical Current Noise on Aluminum Microelectrodes

Abstract

Aluminum disk microelectrodes were used to investigate electrochemical current noise in pH 8.8 borate buffer. The current noise spectra, expressed in terms of the current spectral density, had a characteristic two‐plateau structure in the experimental bandwidth of 0.05–50 Hz, were potential‐independent, and increased proportionally to electrode area. Injection of NaCl solution near the electrode surface, at potentials below that of the onset of pitting corrosion, caused 0.1–1 Hz current fluctuations to appear. From the frequency and area dependence of the current spectral density in the chloride‐free solution, it was concluded that the noise arose from a number of discrete, approximately evenly distributed voltage noise sources positioned electrically in series with the inner barrier layer of the oxide film. A mathematical model for the current noise was developed which described a physical mechanism for noise production based on fluctuations in the widths of cracks or pores in the outer part of the surface film. The model was consistent with the observed area and frequency dependence of the current spectral density, suggesting that the physical process it described is a possible mechanism of noise generation. It could not be determined whether the noise sources were isolated defects or flaws, or pores in an outer precipitated portion of the oxide film. © 1999 The Electrochemical Society. All rights reserved.

Electrochemical noise and impedance study of aluminium in weakly acid chloride solution

“…Types of system which have been analysed are many, such as iron and aluminium and its alloys [13][14][15], coatings on metal substrates [16][17][18][19], erosion-corrosion [20] and microbiologically influenced corrosion [21,22]. The increased interest in the analysis of electrochemical noise is due to the low cost of the equipment, to the possibility of measurements in situ and to the lack of intrusiveness [23,24].…”

Análisis de los transitorios de ruido electroquímico para aceros inoxidables 316 Y – DUPLEX 2205 en NaCl Y FeCl

“…El valor de la raíz media cuadrática (RMS) de la amplitud de estos eventos o desviación estándar se ha visto que provee la huella dactilar de la cantidad de metal disuelto, dependiendo de la combinación metal-medio ambiente. Las fluctuaciones parecen estar ligadas a variaciones en la velocidad de las reacciones anódica y catódica, como consecuencia de los procesos estocásticos (rompimiento y repasivación de la película pasiva) y determinísticos (formación y propagación de picadura) [12][13][14] .…”

“…El concepto de ruido electroquímico presenta un comportamiento inversamente proporcional al intervalo de frecuencia de las oscilaciones, a menor frecuencia mayor amplitud, pudiendo los procesos de corrosión ser investigados mediante la observación del Ruido Electroquímico [8][9][10][11][12][13][14][15][16] . En el caso de la corrosión por picaduras, el cual es un caso especial de la corrosión localizada, existen varios méto-dos para el análisis de los datos de ruido, entre los más populares están los métodos estadísticos como el índice de picado y la densidad de potencia espectral (o análisis espectral).…”

Electrochemical noise analysis of corrosion of pure aluminium in alkaline solution in the presence of SO42− ion, NO3− ion and Na2S additives

“…However, the conventional analysis methods such as statistical analysis method [8,9] and spectral analysis method [10][11][12] did not allow us to distinguish between these stochastic phenomena.…”