Comparison of various electrochemical methods for monitoring steel corrosion in a model alkaline solution containing chlorides and IFKhAN-80 inhibitor

Corrosion of metals in electrolyte solutions obeys the laws of electrochemistry. Therefore, methods based on electrochemical measurements can be used to monitor the state of corrosion processes, although they are indirect, unlike the method of determining the corrosion rate by weight loss. An earlier publication in this journal reviewed the principles of electrochemical methods used for corrosion monitoring and described computer programs for implementing these methods in laboratory research. The publication discusses practical examples of the application of these methods to monitor changes in the corrosion state of carbon steel over time in a model alkaline solution containing chloride ions and the IFKhAN-80 inhibitor. It was found that the Stern–Geary coefficients, which make it possible to associate the corrosion current (and rate) with the polarization resistance, in this system turned out to be 2 or more times lower than the fixed value of 26 mV adopted for automatic corrosion meters based on the measurement of linear polarization resistance. That is, the results obtained on these devices (and with the CorrMeter software that emulates their operation) turn out to be overestimated, although they allow us to monitor the change in the relative corrosion rate over time. It has been shown that a strong inhibitory effect after the addition of IFKhAN-80 to the solution is detected by all the methods studied. It consists in ennobling the potentials of corrosion and passivation of steel manifested in an increase in its polarization resistance by more than an order of magnitude. Methodological issues related to the application of these monitoring methods and the interpretation of their results are discussed.