Corrosion resistance and microstructure of zircaloy-4 subjected to ion irradiation

To investigate the effect of the damage on the corrosion resistance and microstructure of zircaloy-4, irradiation with three types of ions including Ar, Kr and Xe ions has been respectively performed with a fluence range from I X 10(14) to I X 10(16) ions/cm(2). Potentiodynamic polarization measurements were employed to evaluate the corrosion resistance of zircaloy-4 in a IN H2SO4 solution at room temperature, and transmission electron microscope (TEM) was used to analyze the change of microstructures in the surface layer. Corrosion tests show the same trend in polarization curves of the samples respectively irradiated with At, Kr and Xe ions, that is, with the increase of irradiation dose, the passive current density first increasing and then decreasing quickly, while the natural corrosion potential decreases first and then increases rapidly. However, the critical point where the corrosion properties are transformed from damage stage to protection stage, exhibit the distinct diversity among the irradiation fluences. This work indicates that the critical point is determined not by irradiation dose, but by damage level. TEM analyses employed to demonstrate crystalline-to-amorphous transformation process help to investigate the mechanism of the corrosion properties of zircaloy-4 samples irradiated with various doses. (C) 2003 Elsevier B.V. All rights reserved.