Electrochemical noise measurements, corrosion inhibitors

If the system under study is in a transitional state, or inherently unsteady because of local corrosion, EIS measurements will be unstable and noisy as well. Systems that exhibit this kind of behavior consist of passive metals in an environment that has a destructive effect on the passive layer (stainless steels and valve metals (such as aluminum)). Inhibitors (both inorganic and organic) have been observed to "tame this noisy behavior. However, in such cases, electrochemical noise measurements may be more indicated. 

The methods of measuring corrosion rates in the course of testing corrosion inhibitors are conventional weight loss, electrochemical techniques such as linear polarization resistance, potentiodynamic polarization, AC impedance, and electrochemical potential or current noise. 

Variously designed weight-loss coupon, electrochemical and surface analytical techniques have been utilized in REM-based corrosion inhibitors and conversion coatings research. In particular, electrochemical techniques including EIS and polarization measurements have been widely used to evaluate corrosion inhibition by REM compounds under various environmental conditions. Relatively less attention has been paid to the evaluation of localized corrosion inhibition by REM-based compounds, probably because of methodological difficulties and complexities in making accurate localized corrosion rate measurements. Recently developed techniques such as the scanning probe techniques, electrochemical noise analysis and the wire beam electrode are expected to be useful tools in further REM inhibitor research. 

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