Abstract
Corrosion kinetic parameters play an important role in researchers’ ability to understand and predict corrosion behavior. The corrosion kinetic parameters of structural steel Q345B specimens immersed in 3.5wt% NaCl solution for 1–2 h were determined using linear polarization resistance (LPR), Tafel-curve multiparameter fitting, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) methods. The advantages and disadvantages of each method were investigated and discussed through comparative investigation. Meanwhile, the average corrosion rate was examined using traditional coupon tests. The results showed that the corrosion current density values estimated by EFM at a base frequency of 0.001 Hz and those obtained by Tafel-curve four-parameter fitting (TC4) are similar and consistent with the results of coupon tests. Because of their slight perturbation of the corrosion system, EIS and EFM/TC4 in collaborative application are the recommended techniques for determining the kinetics and the corresponding parameters for the homogeneous corrosion of the naked metal. In our study of the electrochemical kinetics, we obtained much more abundant and accurate electrochemical kinetic parameters through the combined use of different electrochemical methods.
Highlights
Metal corrosion is primarily an electrochemical process involving metal oxidation and simultaneous reduction of some other species [1], where corrosion current is one of the most important kinetic parameters
A comparison of the results for the specimens immersed for different durations reveals that the average corrosion rate tends to decrease slightly after the first 24 h of immersion; in addition, the fluctuation ranges of the error bars in Fig. 2 increase with increasing immersion time, which is attributed to increasing influence of the corrosion products
For the sake of consistency of immersion time, the coupon corrosion rate corresponding to 12 h of immersion time, 12.53 μA·cm–2, was chosen for the comparative study with other techniques
Summary
Metal corrosion is primarily an electrochemical process involving metal oxidation and simultaneous reduction of some other species [1], where corrosion current is one of the most important kinetic parameters. Many electrochemical techniques for estimating corrosion kinetic parameters have been developed, including linear polarization resistance (LPR) [22,23,24,25], potentiodynamic polarization [5,6,26,27,28], electrochemical noise (ECN) [2,4,29], electrochemical impedance spectroscopy (EIS) [30,31,32,33], and harmonic distortion analysis [34,35,36]. Several approaches, including LPR, EIS, the Tafel-curve multiparameter fitting method, electrochemical frequency modulation (EFM), and coupon tests, were used to evaluate the corrosion kinetic parameters for a comparative investigation. A Sartorius BSA124S electronic analytical balance with an accuracy of 0.0001 g was used in the coupon tests
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