## 1 Introduction
For instance, the different phases in steel can promote micro-galvanic couples that will promote enhanced corrosion kinetics [29; 30]. Some researchers have worked on studies of structural steels after simulated-fire exposure, however, further research is still needed [31]. The existing studies only observe the post-fire mechanical behavior, no prior exposure behavior nor corrosion behavior was reported [27; 31]. Very limited studies were found regarding corrosion performance of heat treated carbon steel reinforcements [28]. Recent studies have revealed that pearlite was the most susceptible phase to corrosion initiation in chloride contaminated pore solution [32]. Different heat treatments were applied to carbon steel rebars exposed to concrete pore solution to study the chloride threshold. Furthermore, normalizing treatment showed superior passivation performance in non-chloride contaminated electrolytes due to further absorption of hydroxide ions [32]. The chloride threshold values obtained were 0.8, 1.3, and 1.5 M [Cl\({}^{-}\)] for the normalized, as-received and cyclic-heat treated rebars, respectively [32]. In a different study, [PERSON] et al. examined the influence of the microstructure of thermomechanically processed rebars on the corrosion behavior in concrete pore solution. Results showed higher \(i_{\text{corr}}\) values for the samples containing martensite with similar \(E_{\text{corr}}\) values [33]. Thermomechanical treatments on different alloys exposed to 3.5% NaCl showed the effect of the heat treatment on corrosion behavior, showing lower corrosion rates after the treatment [34]. Corrosion studies in different electrolytes, such as the one performed by [PERSON] et al., found that cementie promotes corrosion of steel in solution [35]. In a more recent study, [PERSON] et al. found that the presence of martensite also promotes higher dissolution kinetics due to galvanic couples [36]. In a study performed by [PERSON] et al., a thermal treatment promoted the formation of a dual-phase steel and the corrosion behavior in concrete pore solution was studied [37]. Results showed an enhanced pitting potential as well as lower pit density for the thermal processed specimen, exhibiting a pitting potential >200 mV\({}_{\text{SCE}}\) compared to \(\sim\)100 mV\({}_{\text{SCE}}\) for the conventional rebar [37]. This showed how the presence of ferrite and martensite enhances the corrosion resistance in alkaline media. Similarly, [PERSON] et al. found that thermomechanically treated samples containing martensite and ferrite showed no corrosion products after 32 weeks of exposure compared to the active corrosion observed on the as-received reinforcement [38]. However, another study showed how martensite promotes pitting corrosion [39]. Due to the lack of agreement on the corrosion behavior of the different phases, further research is necessary to understand the corrosion mechanisms of thermomechanically processed steel reinforcements in alkaline media. This study aims to evaluate the chloride induced corrosion behavior of thermomechanically treated rebars in fly ash geopolymer. In this regard, prior microstructural analysis was performed. Afterwards, electrochemical testing, including cyclic potentiodynamic polarization curves (CPP) and electrochemical impedance spectroscopy (EIS), was used to characterize the electrochemical response of the rebar exposed to synthetic FA electrolyte solution. Finally, surface analysis was performed to evidence the enhanced corrosion rates observed in martensitic carbon steel in synthetic FA pore solution containing 0.6 M NaCl.