Corrosion of steel reinforcement in reinforced concrete (RC) structures is a major factor compromising structural integrity and service life. While non-destructive evaluation (NDE) techniques such as ultrasonic testing are commonly used to detect cracks and voids, corrosion-specific detection remains underexplored, and simulation-based investigations are limited. This study presents a preliminary simulation-based analysis of the effect of corrosion layer on the ultrasonic wave propagation in RC structures. A two-dimensional model was developed in COMSOL Multiphysics® to simulate ultrasonic pulse propagation in both healthy and corroded configurations under identical conditions. The corrosion defect was represented by a rust layer surrounding the steel, introducing acoustic impedance mismatches with the surrounding materials. A modulated Gaussian ultrasonic pulse was applied at the transducer, and time-domain responses were analyzed to evaluate the effects of corrosion on wave amplitude. Simulation results indicate that the presence of corrosion significantly alters ultrasonic signal characteristics. The presence of the rust layer caused localized wave scattering and reflection, resulting in high-amplitude peaks and repeated defect-related features in the time-domain response. These changes demonstrate that ultrasonic waves are sensitive to corrosion-induced material degradation, suggesting potential for early detection of corrosion in RC structures.