Sensing localised corrosion by means of electrochemical noise detection and analysis

Abstract

This paper provides a brief review of developments in localised corrosion sensing by means of electrochemical noise detection and analysis. After a bird"s eye view of traditional techniques of detecting localised corrosion, electrochemical noise phenomena and methods including noise signatures and noise resistance are briefly reviewed. Noise signatures refer to characteristic patterns in corrosion potential and current fluctuations that are recognised to be indicators of localised corrosion. Noise resistance is defined as the ratio of the standard deviation of potential noise to the standard deviations of current noise that was proposed as a means of determining the rates of general corrosion. The scope of this review is on various forms of electrochemical noise based localised corrosion sensors, with particular focus on an electrochemically integrated multi-electrode array namely the wire beam electrode (WBE). The WBE is a unique localised corrosion sensor that not only detects noise signatures and noise resistance, but also provides unprecedented spatial and temporal information on localised corrosion. Typical experiments are presented to illustrate the applications of WBE sensors.

Analysis of electrochemical noise measurement on an organically coated metal

“…iron dissolution (2Fe → 2Fe ++ + 4e), oxygen reduction (2H 2 O + O 2 + 4e → 4OH − ) as well as the effect of this fluctuation on the electrochemical potential of system. Much work has been done on bare (uncoated) metal ENM [1][2][3][4][5] showing that Rn is a reliable measure of corrosion resistance and that EN data may be able to determine the type of corrosion [6][7][8]. However when it comes to metal coated with an organic coating, although the ease with which the above electrochemical reactions go on may well control the rate with a defective organic coating, what is more commonly found is that the rate of transport of ions (e.g.…”

A critical review of electrochemical noise measurement as a tool for evaluation of organic coatings

“…Individual distribution maps of ECN and EPN were produced for identifying the anodic and cathodic areas [112]. Also combining these two maps resulted in the distribution map of Rn which was shown to conform nicely with the local distribution of corrosion [8].…”

“…[5,6], showing how Rn is a measure of corrosion resistance. Also mechanistic information about the corrosion process of a bare (uncoated) metal has been acquired through analysis of electrochemical noise data using statistical methods [7][8][9]. Note that in this kind of work, special care must be taken in normalizing the Rn per unit of exposed surface area as this is required for the calculation of an absolute corrosion rate [10,11].…”

“…It has been successfully implemented as an effective electrochemical technique in combination with wire-beam multi-electrodes where a quick examination of a large number of electrodes is required [8,40,41]. It also offers the advantage of being a noninterfering measurement compared to DC techniques which may alter the system from the steady state.…”

Corrosion monitoring of type 304L stainless steel in nuclear near-high level waste by electrochemical noise

“…A simple visual examination of the time record gives distinct noise characteristics for various processes like passivation, uniform and localized corrosion [8,[10][11][12][13]. Typical representation of the EN time records taken for AISI type 304L SS in 3 N HNO 3 , 304L SS, and sensitized 304 SS in near-HLW solution are shown in Figs.…”