2.2. Electrochemical Measurements

A three-electrode cell was used for the electrochemical experiments. The potentials were measured against Ag/AgCl/KCl_sat as a reference electrode (Ref), while a twisted platinum wire (Φ = 0.5 mm, L = 10 cm) was used as counter-electrode.

The electrochemical measurements were carried out using a Princeton Applied Research (PAR) model 2273 potentiostat (Princeton Applied Research, Oak Ridge, TN, USA, 2008). Before each measurement, the working electrodes were left for at least 1 h in the corrosive solution to obtain stable open circuit potentials (OCP). In each experiment, a fresh working electrode was used, and two measurements were performed to ensure the data reproducibility.

Potentiodynamic polarization curves were recorded at a constant sweep rate of 10 mV min⁻¹, in a wide potential range of ±250 mV vs. OCP, from the cathodic to the anodic direction.

Impedance spectra were recorded at OCP, in the frequency range of 100 kHz–10 MHz, at 5 points per hertz decade, using an alternating voltage amplitude of ±10 mV. The experimental impedance data were modeled using ZSimpWin 3.21 software (EChem Software, MI, USA).

The electrochemical measurements were performed at room temperature, in the electrolytes under non-stirred and naturally aerated conditions.