## 3 Results and Discussion
A decrease in the \(E_{\text{corr}}\) values from \(-\)0.500 to \(-\)0.561 and \(-\)0.423 V\({}_{\text{SCE}}\) was observed, as well as an increase in the corrosion current density (\(i_{\text{corr}}\)) values from 2.13 \(\times\) 10\({}^{-6}\) to 1.84 \(\times\) 10\({}^{-6}\) and 2.09 \(\times\) 10\({}^{-5}\) A/cm\({}^{2}\) for as-received, normalized, and annealed sample, respectively; calculated from the intersection of the anodic (\(\beta_{\text{a}}\)) and cathodic (\(\beta_{\text{c}}\)) Tafel slopes. The higher dissolution kinetics shows the influence of the aggressiveness of the environment as well as the thermomechanical treatment [44; 45]. Furthermore, the higher anodic dissolution kinetics observed for the annealed sample can be explained by the more coarse grains present [46]. However, at this alkaline pH (13.6), the degaussivation induced  
Figure 4: Open circuit potential obtained during 1 h for the sample exposed to FA pore solution containing 0.6 M NaCl with: (**a**) slow cooling rate, and (**b**) fast cooling rate. by the chlorides is not severe as all three specimens show a negative hysteresis on the backward scan, indicating that the CS rebar samples remained in a passive state. Regarding the faster cooling rate samples exposed to synthetic FA pore solution, the most active behavior is observed by the oil quenched sample as the curves shift toward higher current densities (_i_) as well as toward lower potentials, shown by Figure 5b. This can be explained by the mixed bainite and martensite microstructure. A Flade potential is observed for the quenched samples around \(-0.45\) V\({}_{\text{SCE}}\). All samples display a negative hysteresis loop as well as no clear sign of pitting corrosion. The samples that undergo subcritical annealing show lower corrosion rates and a similar corrosion behavior in between, being the most active the annealed water quenched sample due to presence of martensite and bainite in the microstructure [47]. Previous studies showed how a subcritical annealing enhanced the pitting corrosion resistance [48]. Table 2 shows the characteristic parameters that were obtained from the CPP for both scan directions and cooling rates. The quenched samples show an \(E_{\text{corr}}\) value around \(-0.50\)\(\pm\)\(0.01\) V\({}_{\text{SCE}}\), similar to the as-received sample but with \(i_{\text{corr}}\) values one order of magnitude higher. Lower \(E_{\text{corr}}\) values are observed for the subcritical annealing process after the quenching, with values of \(-0.60\)\(\pm\)\(0.01\) V\({}_{\text{SCE}}\). An increase in the \(i_{\text{corr}}\) values is observed for the oil  
Figure 5: CPP of thermal treated CS specimens in FA pore solution containing 0.6 M NaCl: (**a**) slow cooling rate, and (**b**) fast cooling rate. quenched sample. \(i_{\rm corr}\) values ranged from 3.18 \(\times\) 10\({}^{-5}\) to 2.20 \(\times\) 10\({}^{-5}\) A/cm\({}^{2}\) for the water and oil quenched samples, respectively. An order of magnitude higher after subcritical annealing is observed, with values of 2.18 \(\times\) 10\({}^{-6}\) and 2.77 \(\times\) 10\({}^{-6}\) A/cm\({}^{2}\) for subcritical annealed water quenched, and subcritical annealed oil quenched, respectively. After the subcritical annealing, a more novel behavior is observed. Thus, indicating the influence on corrosion of the thermomechanical treatment. The samples were in a passive state as the negative hysteresis loop in the backward scan evidenced. In order to further investigate the electrochemical dissolution kinetics of the system, the cathodic oxygen reduction reaction (ORR) was evaluated by means of the calculation of the exchange current density of the ORR (\(i_{\rm 0,ORR}\)). It was obtained via intersecting the cathodic Tafel slope (\(\beta_{\rm c}\)) with the oxygen equilibrium line (O\({}_{2}\) + 2H\({}_{2}\)O + 4e\({}^{-}\) \(\rightleftarrows\) 4 OH\({}^{-}\)).