## 2 Experimental Development
### Electrochemical Tests in Corrosion Loop  
For the dynamic testing, FL was used (Figure 1A). It has a storage capacity of 18 liters. In the loop pipelines, two 1045 carbon steel corrosion coupons were placed, labeled as C1 (the upper area of the pipeline) with a medium-exposed area of 56.5488 mm\({}^{2}\) and as C2 (lower area of the pipeline) with a medium-exposed area of 64.8168 mm\({}^{2}\). To avoid crevice corrosion formation in the coupons, they were carefully sealed with neutral cure silicone, as shown in Figure 1B. Before mounting the coupons, they were glass-polished and weighed with an AUW 220D weighing scale (e = 1 mg; d = 0.1 mg/0.01 mg). Figure 1: (**A**) Corrosion loop and its components; (**B**) coupon. Out of the four inhibitors that were tested at a 150 ppm concentration, Inhibitor 1 was the one that had an efficiency equal to or greater than 90%. The rest of the corrosion inhibitors did not reach a 90% efficiency in any of the tests with the rotating cylinder. The oil company considers that an inhibitor passes the test if its corrosion efficiency is equal to or greater than 90%. Figure 2: Curves obtained through polarization resistance to different rpm of the corrosion inhibitors. Fractographies at 20\(\times\) of the carbon steels tested with the corrosion inhibitors are shown in Figure 3. They were assessed considering the criterion of [PERSON] et al. (2015), which is shown in Table 2, as exclusively requested by the oil company. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Rank** & **Description of Pitting** \\ \hline
0 & No pits. Surface same as for original untreated coupon. \\ \hline
1 &
\begin{tabular}{p{113.8 pt}} Intergranular corrosion on cut edge of coupon, giving a sintered effect; no pits on major surfaces. \\ \end{tabular} \\ \hline
2 & Small, shallow pits on cut edges; no pits on major surfaces. \\ \hline
3 &
\begin{tabular}{p{113.8 pt}} Scattered, very shallow pinpoint pits, less than 25 pits on either surface—that is, front or back. \\ \end{tabular} \\ \hline
4 & More than 25 pits of Rank 3 on either surface. \\ \hline
5 & Ten or fewer pits, 1/332 to 1/16 in. diameter and 1/64 to 1/32 in. deep. \\ \hline
6 & Between 11 and 25 pits of Rank 5. \\ \hline
7 & More than 25 pits of Rank 5. \\ \hline
8 &
\begin{tabular}{p{113.8 pt}} Pits larger than 1/16 in. but less than 1/8 in. in diameter, greater than 1/32 in. deep, 100 or fewer in number. \\ \end{tabular} \\ \hline
9 & Any pitting more severe than Rank 8. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: [PERSON]’s criterion for assessing corrosion levels. Figure 3: Factorographies of the tested graduated cylinders (20\(\times\)). The yellow arrows show the presence of pitting according to [PERSON]’s criterion. Inhibitor 1 exhibited general corrosion, but no major pits were observed; thus, it is considered to be Rank 2, according to [PERSON], whereas in the rest of the tested inhibitors, the surface of the carbon steel revealed abundant pitting. Tests with the NACE solution (Table 3 and Figures 4 and 5) were carried out at a 65 \({}^{\circ}\)C working temperature, saturated with CO\({}_{2}\) 99.995%, at a flow speed of 1.2 m/s equal to an angular velocity of 1100 rpm [40]. The chosen flow velocity was the same as that of the pipeline in the company's oil field. A Cosasco Aquamate Corrater Instrument was used to measure both the electrochemical LPR and the weight-loss corrosion rate. An electrochemical current noise (ECN) form, known as imbalance (unbalance or pitting tendency) was also monitored among the electrodes. This is a useful qualitative instability signal on the surface of the material that coincides with pitting or localized corrosion. Figure 4 shows the corrosion rate and the imbalance rate (pitting tendency), both depending on time for each tested corrosion inhibitor. Inhibitors were added to the solution only once, with an individual concentration of 150 ppm, equal to the concentration used for the RCE tests.