*2.3. Electrochemical Experiments*

The electrochemical experiments were carried out in a 1.2 L high-pressure autoclave (PARR instrument) at different CO2 partial pressures (1, 20, and 40 bar) with a conventional three-electrode system. N80 carbon steel specimen was used as a working electrode, a platinum foil as a counter electrode (CE), and a high-pressure 0.1 M KCl Ag/AgCl probe was used as a reference electrode. To ensure homogeneous mixing, a Teflon-coated blade agitator was used (200 rpm). The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) measurements were carried in a Gamry reference 600 potentiostat/galvanostat electrochemical system after the sample was exposed for 24 h in the tested solution, with and without the presence of 1.0 g L−<sup>1</sup> of GA. The EIS tests were performed over the frequency range of 100 kHz to 10 mHz and amplitude of 10 mV at open circuit potential. The data were then fitted by means of Echem Analyst 5.21 software using the opportune equivalent circuit. The *IE*% was calculated from the polarization resistances (*R*p) determined from the fitting process using the following equation [21,26]:

$$IE\% = \frac{R\_{\text{P}}^{\text{inh}} - R\_{\text{P}}}{R\_{\text{P}}^{\text{inh}}} \times 100\tag{3}$$

where *R*<sup>p</sup> inh and *Rp* are the values of the polarization resistances in the presence and absence of the inhibitor, respectively. The PDP measurements were carried out at a potential of ±−0.3 V from the OCP and a scan rate of 1 mV s−1. The potentiodynamic parameters were determined by means of Echem Analyst 5.21 software. The values of *IE*% were calculated from the measured *i*corr values using the relationship [21,26]:

$$I\text{E\%} = \frac{i\_{\text{corr}} - i\_{\text{corr}}^{\text{inlt}}}{i\_{\text{corr}}} \times 100\tag{4}$$

where *i*corr and *i* inh corr represent the values of the corrosion current densities without and with inhibitor, respectively.
