Abstract: The objective of this research was to analyze the influence of oxidation corrosion layers on the thermal-hydraulic performance of lead-bismuth-cooled fast reactors, focusing on the development of a heat transfer model suitable for oxidized wall surfaces. This is pertinent due to the changes in wall conditions caused by corrosion or protective coatings, which can significantly affect the heat transfer characteristics within the reactor. To achieve this objective, a combination of experimental measurements and numerical simulations was employed in the study. The experimental work involved measuring the roughness of the test section after experiment in lead-bismuth eutectic environment without oxygen control device, which revealed a maximum roughness of 91.5 μm and a relative roughness of 0.004 575. These measurements were crucial as they provided the input parameters for the numerical simulations. The numerical simulations were conducted using ANSYS Fluent and were based on the experimental flow and heat transfer data of lead-bismuth eutectic. A rough wall heat transfer model was utilized, with the wall roughness of the test section as a key input parameter. The simulations were designed to replicate the conditions of the experiments and to assess the impact of wall roughness on heat transfer. The results of the simulations were compared with experimental data, showing a significant agreement when the roughness was accounted for, which validated the numerical model and highlighted the necessity of considering wall roughness in heat transfer relations. The study also observed that the impact of roughness on heat transfer increased with the Peclet number (Pe), indicating the importance of roughness in high-velocity flows. Based on the validated model, the research extrapolates the findings to develop a heat transfer correlation for lead-bismuth eutectic that includes a roughness correction factor. This correlation was formulated to predict the heat transfer characteristics in pipes with different diameters, wall roughness, and flow velocities, providing a comprehensive tool for thermal-hydraulic analysis. In conclusion, the study successfully demonstrates the significant impact of oxidation corrosion layers on the heat transfer characteristics of lead-bismuth eutectic in rough pipes. The developed heat transfer correlation, which incorporates wall roughness, offers a valuable tool for the analysis and design of lead-bismuth-cooled reactors, particularly in scenarios where long-term corrosion effects are a concern. The research contributes to the broader understanding of heat transfer in the presence of wall roughness and provides support for thermal-hydraulic modeling of lead-based reactors.