Evaluation of the Effect of Carbon Dioxide Corrosion Inhibitors on Cavitation Damage Caused during the Ultrasound Test Available to Purchase

A test for evaluating oilfield corrosion inhibitors using ultrasound has been developed recently. This paper describes experiments that have been undertaken to try and determine some of the processes that occur at the electrode surface during the test. Measurements were taken with both polarization resistance and electrochemical impedance spectroscopy techniques during cavitation of carbon steel electrodes in 1 M sodium chloride (NaCl) solution saturated with carbon dioxide (CO₂) in the absence and presence of a corrosion inhibitor. Scanning electron microscopy images were taken of the surfaces following the tests and compared with the electrochemical data. These techniques confirmed that not only can the inhibitor performance be determined in a reproducible manner, it also can reveal that in the absence of inhibitor, the surface becomes roughened due to metal loss. Conversely, in the presence of inhibitor, the data suggests that the inhibitor forms a physical barrier between the metal and solution protecting the surface, producing an electrochemically more homogenous surface at the end of the experiment when compared to the uninhibited case. All electrodes exposed to cavitation developed surfaces that had two distinct regions with very different corrosion products.