## 1 Introduction  
Because of their durability and versatility, reinforced steel bars (rebar) are extensively used in construction. However, corrosion of rebar leads to cracks and spalling on the surface, affecting the safety and durability of reinforced concrete. The main challenge for conventional rebar is how to minimize corrosion due to oxide or passive layer breakdown. The apprehension about chloride-induced corrosion has motivated researchers to focus on carbon materials, such as carbon steel, as reinforcement for concrete. To calculate the required chloride percentage for passivation, three methods are used: the total chloride amount in weight percent (wt. %), the free chloride concentration (Cl%), and the chloride/hydroxide (Cl/OH) ratio [1]. In addition, different methods are used to measure the chloride content percentage, such as electrochemical impedance, potentiodynamic polarization, gravimetric measurement [2; 3; 4; 5; 6; 7; 8; 9; 10; 11]. Failure of the oxide or passive layer is usually due to the reaction of Cl\({}^{-}\) ions with the rebar surface in an appropriate alkaline environment [12; 13; 14; 15; 16]. Various experiments have been conductedto understand the relationship between corrosion rate and Cl% in the environment surrounding rebar reinforcing concrete, especially under alkaline conditions [17; 18; 19; 20; 21; 22], in order to optimize the different conditions and generate a susceptible Cl% suitable for pitting. Studies have reported that Cl% varies depending on many parameters. [PERSON] and [PERSON] [16] showed that the critical Cl% is between 0.01 and 0.04 M in saturated calcium hydroxide and 0.4-0.6 M in simulated concrete pore solution (SCPS-PH-13.5). [PERSON] et al. [18] reported a relationship between the critical Cl% of carbon steel and the solution pH, and Cl% increased from 0.17 M at pH 12.5 to \(>\)0.27 M at pH 13.8 in sodium hydroxide solution. The mechanical performance, reliability, and durability of the rebar surface are significantly affected by its corrosion behavior. [PERSON] et al. [17] described how mechanical properties are affected by pitting corrosion on the rebar surface. A pitting morphology leads to stress concentration, initiating cracks and fatigue failure due to crack propagation. Therefore, analyzing the corrosion behavior of pits is important for estimating the life of reinforced concrete structures [20]. In non-cracked concrete, corrosion of reinforced steel starts from the high-concentration chloride area via an anodic localized reaction. In cracked concrete, corrosion of reinforced steel starts from the area where small anodes formed around the crack line [18]. In active corrosion, macro- and microcell corrosion can exist simultaneously [19]. Many factors affect the corrosion of reinforced steel in cracked concrete, such as concrete composition and resistance, loading, and exposure conditions [20; 23]. The dual-phase (DP) steel microstructure is characterized by a matrix of fine ferrite with S.M.A.Il spots of a second, harder phase--high-strength steel. Although some of bainite or retained austenite might be present, the second phase mainly comprises martensite. The martensite volume fraction ranges between 5% and 30%. Martensite offers significant strengthening, while the ductile ferrite matrix offers good formability [24; 25; 26]. DP rebar acquires its mechanical properties from the two phases [27; 28; 29; 30; 31; 32; 33], and the presence of a dual phase in reinforced concrete structured steel induces good corrosion resistance. Many variables affect the ductility of an element while it is subjected to different loads, especially a bending moment, such as the element material, cross-sectional geometry, and mechanical properties. Especially, for reinforced concrete, these variables are represented by strength, the concrete's mechanical properties, reinforcement ductility, bonding between reinforcement and concrete, cross-sectional geometry, structural details, transverse shear and longitudinal force, and element slenderness.