Corrosion inhibitors electrochemical impedance

There are several experimental techniques that may be used to test the performance of a candidate corrosion inhibitor. Electrochemical testing (e.g. AC impedance and DC polarisation) are the traditional and primary research techniques, whereas weight loss determinations (immersion [45], outdoor exposure, or salt fog/cyclic chamber tests) tend to be used in commercial appUcations [90]. 

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. 

Successful inhibitor tests require suitable corrosion measurement and analysis techniques that are able to correctly record and interpret corrosion rate data. Many testing and monitoring techniques that were developed initially for the diagnosis and prediction of corrosion have been successful employed in laboratory and field corrosion inhibitor testing and research. These techniques include the use of corrosion coupons, solution analysis, electrical resistance probe, polarization resistance, electrochemical impedance spectroscopy and many other physical, electrical and electrochemical methods. 

The anticorrosion performance of these coatings assessed by electrochemical impedance spectroscopy shows that the lower impedance was obtained when BTA was directly added to the sol-gel matrix, whereas the best performance was achieved with inhibitor-doped TiO coated with a hybrid film. In terms of active corrosion protection, there is a periodic decrease/increase of impedance associated with the breakdown followed by the self-healing of the intermediate oxide layer. SVET was employed to study the self-healing ability of bi-layer systems at the micro level. The measurements of local corrosion current evolution in the zones of artificial defects have demonstrated well-defined corrosion activity on the sirrface of AA2024 coated with sol-gel film only, while no corrosion activity was revealed even after 24 hours on the alloy treated with a bi-layer system. The reported resirlts show that the adsorbed inhibitor is leached out from the porous... 

The impedance spectroscopy of steel corrosion in concentrated HC1, with and without inhibitors, exhibit relatively straightforward electrochemical phenomenology and can be represented by simple equivalent circuits involving primarily passive electrical elements. Analysis of these circuits for steel corroding in HC1 per se reveals that the heterogeneity of the surface is established rapidly and can be simulated with a simple electrical circuit model. 

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