Effects of Heat Treatment on Zirconium Corrosion Behavior

Abstract Zirconium is extensively used in chemical processing due to its exceptional resistance to corrosion, particularly in nitric acid environments. However, variations in microstructure—such as grain size differences resulting from heat treatment—can impact its corrosion behavior. This study explores how different heat treatments, designed to produce a range of grain sizes and microstructures, affect the corrosion performance of Zirconium 702 tubing. Electrochemical techniques including open circuit potential (OCP), linear polarization resistance (LPR), and cyclic potentiodynamic polarization (CPP) were employed in 70 % HNO3 at 50 °C and 90 °C. To correlate corrosion behavior with microstructural features, metallurgical characterization was conducted using optical microscopy and scanning electron microscopy (SEM). The corrosion test findings show no pitting at either 50 °C or 90 °C. Annealed specimens exhibited improved passive film stability and lower corrosion rates at elevated temperature compared with the non-annealed condition. These results highlight the importance of achieving a fully recrystallized microstructure through controlled annealing, which enhances corrosion resistance under aggressive condenser environments. Testing results provide insights into how heat treatment and resulting microstructures influence corrosion susceptibility and passivation behavior in Zirconium 702.