The widespread use of calcium sulfoaluminate cement (CSA) for rapidly repairing marine structures exposed to high chloride levels has spurred limited investigation into the corrosion behavior of reinforcements in low-pH CSA systems. To address this knowledge gap, researchers conducted a comprehensive study on the impact of primary ions within CSA (OH−, SO42−, and Al(OH)4-) on steel rebars in simulated pore solutions (SPSs). The investigation employed various analytical methods such as Mott-Schottky/cyclic polarization curves, corrosion current, impedance spectrum analyses, and microstructural examinations. The results demonstrate that SO42− diminishes the corrosion resistance of reinforcements by depassivating them, consequently reducing the critical chloride concentration (Ccrit). However, this influence is mitigated with elevated OH− or Al(OH)4− concentrations. Furthermore, the presence of Al(OH)4- in the pore solution contributes to an increased Ccrit by stabilizing alkalinity via OH− hydrolysis. Based on the empirical findings, the researchers developed an empirical formula for Ccrit, offering insights into estimating the service life of CSA-based concrete structures in real marine environments.