Abstract: The effect of Zn addition on general corrosion and metal release behavior of alloy 690 were investigated in simulated pressurized water reactor (PWR) primary water with 0, 10 and 40 ppb Zn additions. The corrosion rate and the metal release rate were calculated by weight loss method after3000 h exposure. The surface and cross-sectional morphology, thickness and element distribution along the oxide film were analyzed by scanning electron microscope (SEM) and transmission electron microscope-energy disperse spectroscopy (TEM-EDS). The crystallographic structure of the outer and inner oxides was identified using atomic-resolution TEM imaging with fast Fourier transformation (FFT). The results indicate that the corrosion rate, metal release rate and oxide film thickness of alloy 690 all decreased with the increase in Zn concentrations. The addition of 10 ppb Zn results in an approximately 18% reduction in the average corrosion rate and 14% reduction in the metal release rate, which further decreases by about 35% with an increase in Zn concentration to 40 ppb. Meanwhile, the average thickness of oxide film of alloy 690 significantly decreases from 110 nm to 25 nm when the concentration of Zn is increased from 0 to 40 ppb. The microstructural analysis of the oxide film indicates that the oxide film of alloy 690 exhibits a three-layer structure in 40 ppb Zn addition condition. The outermost oxide film has less Zn and is primarily composed of (Zn, Ni)Fe₂O₄. The intermediate oxide film contains much more Zn with a structure of Zn(Cr, Fe)₂O₄. The innermost oxide film at the oxide/metal (O/M) interface is mainly composed of Cr₂O₃. In PWR primary water, the free energy required for the formation of spinel ZnCr₂O₄ is lower than that of FeCr₂O₄ and NiCr₂O₄, and ZnCr₂O₄ exhibits a much lower solubility compared to other spinel, which results in its greater stability within the oxidation film. Meanwhile the Zn²⁺ promotes the denser Zn(Cr,Fe)₂O₄ outer and intermediate oxide film formation by filling the cation vacancies and replacing the Ni²⁺ and Fe²⁺ in spinel. In summary, the Zn addition can significantly enhance the stability and compactness of the oxide film on alloy 690, thereby retarding the outward diffusion of metal ions and inward diffusion of oxygen ions. Additionally, it reduces the oxygen partial pressure at the O/M interface, promoting the formation of an inner layer composed of Cr₂O₃. Consequently, this effectively suppresses corrosion and minimizes metal release from alloy 690 in PWR environments.