Electrochemical noise (ECN) is the generic term given to fluctuations of
current
Currents, Current or The Current may refer to:
Science and technology
* Current (fluid), the flow of a liquid or a gas
** Air current, a flow of air
** Ocean current, a current in the ocean
*** Rip current, a kind of water current
** Current (stre ...
and
potential
Potential generally refers to a currently unrealized ability. The term is used in a wide variety of fields, from physics to the social sciences to indicate things that are in a state where they are able to change in ways ranging from the simple r ...
. When associated with
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
, it is the result of stochastic pulses of current generated by sudden film rupture, crack propagation, discrete events involving metal dissolution and hydrogen discharge with gas bubble formation and detachment. The technique of measuring electrochemical noise uses no applied external signal for the collection of experimental data.
The ECN technique measures the signal perturbations which are low level fluctuations of the corrosion potential between two nominally identical electrodes which can be used in the mechanistic determination of corrosion type and speed. The fluctuations are usually of low amplitude, less than 1
mV and of low frequency bandpass filtered
RMS value (
DC and high frequency
AC components removed). The noise corresponds with the low level frequency noise (differential of the ZRA) signal but has a much lower amplitude when general corrosion is involved. The major source of noise can be ascribed to macroscopic random-stochastic phenomena. They include partial faradaic currents adsorption / desorption, surface coverage, corrosion cracking and mechanical erosion processes. A common feature of this 1/f Poisson spectra is that it differs from the "white" Gaussian noise in which accuracy increases as the square root of the measurement time.
The technique considers the reactions occurring at the metal–solution interface and suggests two currents flowing on each electrode as a result of the anodic and cathodic reactions. Once regarded as a source of bias and error that compromised electrochemical measurements it is now regarded as a rich source of information. The technique is widely used within the
Corrosion engineering
Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to mana ...
world as a useful
Corrosion Monitoring technique.
The ECN phenomenon belongs to the general category of random low frequency stochastic processes described by either probability density function equations or in statistical terms. These random processes are either stationary or non-stationary. The first moments of a stationary process are invariate with time.
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Electrochemistry
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