With the rapid growth of the international crude oil shipping industry, ensuring the safety of oil tanker transportation has become a critical concern. The cargo oil tank (COT), the primary structure for storing crude oil, is particularly susceptible to corrosion, with the inner bottom plate being a key site for failure and potential oil leakage. Low-alloy corrosion-resistant steel, mandated by the International Maritime Organization as an alternative to traditional anticorrosion coatings, faces challenges in China due to insufficient corrosion resistance, limiting its long-term applicability in COTs. Enhancing the intrinsic properties of ship plate steel while minimizing costs is therefore crucial for improving its corrosion resistance and mechanical performance. In the simulated acidic Cl^- environment of a COT bottom plate, a micro-galvanic couple forms between ferrite and cementite in pearlite, with ferrite acting as the anodic phase and cementite as the cathodic phase. Over time, accumulated cementite thickens on the surface, increasing the anode/cathode area ratio and accelerating the corrosion rate due to intensified micro-galvanic effects. To mitigate this, a deformation spheroidization process was employed to refine the microstructure without additional alloying elements. By optimizing forging and heat treatment parameters, a tempered sorbitic microstructure was achieved in T8 steel. Microstructural evolution was characterized using SEM and EBSD, while mechanical properties were assessed through microhardness testing, tensile experiments, and fracture morphology analysis. Corrosion behavior before and after optimization was examined via mass loss tests, electrochemical analysis, and corrosion product characterization. The results indicate that spheroidization heat treatment enhances the strength, plasticity, and toughness of T8 steel through grain refinement, dislocation strengthening, and dispersion strengthening. The transformation of bulk layered cementite into fine-grained cementite effectively suppresses its accumulation on the surface during corrosion, mitigating the accelerating effect of micro-galvanic corrosion. Consequently, the corrosion resistance of T8 steel in the simulated COT environment was significantly improved. This study demonstrates a cost-effective approach to enhancing both the mechanical properties and corrosion resistance of ship plate steel through microstructural control, offering new insights for the development of corrosion-resistant materials for cargo oil tanks.