Electrical resistance measurements, corrosion inhibitors

An electrical resistance methods which directly measures loss of metal from a probe installed in the corrosive system under study is described in Section 19.3. It is reported that corrosion equivalent to a thickness loss of as little as 2-5 X 10 cm can be detected . This technique is most useful as a means of monitoring steps taken to reduce corrosion, e.g. by inhibitors, or to detect changes in the corrosivity of process streams. Electrical methods of determining corrosion rates are considered subsequently. 

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. 

Some work [23-25] has been done in which an occluded cell condition is set up, with electrically isolated anode and cathode connected through a zero resistance ammeter. The current flow between the electrodes is proportional to the corrosion occurring on the 2inode. This technique provides a measure of the rate of corrosion penetration in occluded areas. With this technique, it is possible to allow the corrosion reaction to start (forming oxide deposits) and then determine the ability of different inhibitors to control the corrosion in the presence of the deposits. 

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