Abstract: The primary objective of this study is to reveal the corrosion failure mechanism of typical accident-tolerant fuel (ATF) Cr-coated claddings under deviated water chemistry conditions in the primary loop of pressurized water reactors (PWRs). Given the critical role of Cr coatings in enhancing the corrosion resistance of fuel claddings, understanding their dissolution behavior under varying high-temperature and high-pressure water environments is essential for ensuring the long-term safety and reliability of nuclear power plants. Pure metallic Cr was selected as the research object in this work, as it serves as the key component of the protective coating and its corrosion behavior directly reflects the performance of the entire Cr-coated cladding system. To achieve the research goal, a series of corrosion dissolution experiments was conducted under different temperatures and dissolved oxygen (DO) concentration conditions. A high-temperature and high-pressure water micro-flow corrosion loop with a Ti inner lining was employed to simulate the actual operating environment of the PWR primary loop. This experimental apparatus ensures the stability of temperature, pressure, and water chemistry parameters throughout the experiment, which is crucial for obtaining accurate and reproducible corrosion data. The electrical conductivity at the outlet of the loop was monitored in real-time to continuously track the dissolution process of Cr. Additionally, inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the concentration of Cr ions in the solution, providing a reliable method to verify the dissolution rate data obtained from the electrical conductivity monitoring. For the data analysis and model establishment, the Arrhenius equation and Butler-Volmer (B-V) equation were integrated to develop a mixed potential model describing the corrosion dissolution behavior of Cr in high-temperature and high-pressure water. This mixed potential model takes into account both the electrochemical reactions and the temperature-dependent kinetic processes, enabling a comprehensive understanding of the corrosion mechanism. To further improve the accuracy of the model, a genetic algorithm was applied to optimize the model parameters, and the optimized model was then used to fit the experimental data. Through this process, a Cr dissolution kinetic model that considers the coupled effects of temperature and DO concentration was successfully constructed. The research results show that there is a positive correlation between the Cr dissolution rate and temperature. Specifically, when the temperature exceeds 150 ℃, the dissolution rate of Cr increases significantly with the increase in temperature, demonstrating a strong temperature dependence. This phenomenon can be attributed to the accelerated electrochemical reaction kinetics and the increased mobility of ions at higher temperatures, which promote the dissolution of the Cr surface. Regarding the effect of DO, the presence of DO significantly promotes the corrosion dissolution process of Cr. In the deaerated environment, the dissolution of metallic Cr is barely detectable, indicating that oxygen plays a critical role in initiating and accelerating the corrosion reaction. When the DO concentration exceeds 300 ppb, a notable increase in the Cr dissolution rate is observed, and the dissolution rate continues to increase with the further increase in DO concentration. This result suggests that the DO concentration is a key factor controlling the corrosion rate of Cr in the PWR primary loop environment, and effective oxygen control is essential for mitigating the corrosion failure of Cr-coated claddings. The kinetic prediction model of Cr dissolution successfully described the coupling effect of temperature and DO, enabling a quantitative evaluation of the corrosion failure of metallic Cr under deviated water chemistry conditions.