## 3 Results and Discussion  
The microstructural analysis revealed that each thermomechanical treatment produced a different microstructure according to the cooling rate. Figure 2 shows the heat-treated samples that did not show martensite. The as-received sample shows the pearlitic microstructure with large cementite areas (see Figure 2a). The effect of the cold rolling process at the edge of the rebar can be observed, displaying more refined grains and less cementite (see Figure 2b). The annealed sample shows a considerably larger grain size in both the center and the edge (see Figure 2c,d). After the normalizing treatment, it can be seen that the microstructure in the center of the rebar is similar to the as-received sample, showing more uniform and refined ferrite grains (see Figure 2e). However, the edge of the rebar shows much smaller grains as well as Widmansstatten ferrite (see Figure 2f) [41]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline
**C** & **Mn** & **S** & **Cu** & **P** & **Ni** & **Cr** & **Si** & **Mo** & **V** & **Fe** \\ \hline
0.28 & 1.08 & 0.043 & 0.37 & 0.019 & 0.16 & 0.16 & 0.20 & 0.050 & 0.0379 & Bal. \\ \hline \end{tabular}
\end{table} 
Table 1: CS elemental composition in wt.%. For the fast cooling rate, water quenching developed a full martensitic microstructure as the most aggressive cooling rate (see Figure 3a,b). The oil quenched experienced a similar microstructure with some visible ferrite (see Figure 3c,d). After the quenching process, some samples underwent subcritical annealing at 500 \({}^{\circ}\)C. After the subcritical annealing, the water quenched sample displayed low bainite in both regions, evidenced by the feather-like bainite in Figure 3e,f [42]. After the subcritical annealing, the oil quenched sample showed a mixture of bainite and martensite in both regions of the rebar (see Figure 3g,h). The OPC plots were monitored for 1 h as shown in Figure 4, it can be observed that the OCP stabilized within \(\pm\)25 mV range after 3000 s, indicating that the samples reached steady state. The recorded OCP values are in good agreement with the \(E_{\text{corr}}\) values obtained during the CPP test (see Figure 5). Figure 3: Micrography of rebars after thermomechanical treatments (\(\times\)100): Water quenched ((**a**) center, (**b**) edge), Oil quenched ((**c**) center, (**d**) edge), subcritical annealing after water quenching ((**e**) center, (**f**) edge), and subcritical annealing after oil quenching ((**g**) center, (**h**) edge). Figure 2: Micrography of rebars after thermomechanical treatments (\(\times\)100): As received ((**a**) center, (**b**) edge, Annealing ((**c**) center, (**d**) edge), and Normalizing ((**e**) center, (**f**) edge). The CPP curves for the as-received and moderate cooling rate samples immersed in synthetic FA pore solution containing 0.6 M NaCl can be seen in Figure 5a. A more active behavior is observed in the annealed sample as the curves shift towards higher current densities (_i_) as well as towards lower potentials. This can be explained by the larger grain size. A Flade potential (\(E_{t}\)) associated with the passive layer formation at high pH is observed for the as-received sample around \(-\)0.45 V\({}_{\text{SCE}}\)[43]. All samples display a negative hysteresis loop as well as no evident sign of pitting corrosion. This is denoted by the absence of a pitting potential, or a sudden increase in the current density value [16]. The as-received and normalized samples show a similar corrosion behavior, of which the most active is the as-received sample due to the cold rolling process. This process generated a smaller grain size as well as martensite near the corrugated area.