The specimens used for electrochemical impedance tests were the
same as those used for potentiodynamic polarization tests. A three electrode
system was used in EIS measurement. The test parameters
were as follows: 10 mV perturbation and five points per decade. Frequency
range was from 100 kHz to 10 mHz. Before EIS test proceeded,
the potential of specimens reached a stable state in the solution. The
experimental results were interpreted based on an equivalent electrical
circuit by using a suitable fitting procedure of ZSimpWin.