저널

The nodular corrosion behavior of Zircaloy-4 alloy was investigated by autoclave test at 50$0^{circ}C$ under 1500 psi for the specimens quenched into water from $700^{circ}C$, 80$0^{circ}C$, 90$0^{circ}C$, and 105$0^{circ}C$. It was observed that the corrosion resistance of Zircalloy-4 specimen increased with increase in annealing temperature, and annealing at $alpha$-region temperatures resulted in nodular corrosion while annealing at the temperature range of $alpha$+$eta$ and $eta$ did not show nodular corrosion. It was also found that the size of nodule formed on the surface of the specimens increased with increase in exposure time in autoclave, but the total number of nodule remained uncha-nged. The corrosion of furnace-cooled specimens progressed mostly in the interior of grains where Fe and Cr alloying elements were largely depleted during the cooling process. However, the grain boundary seemed to act as a barrier to the nodular corrosion. From combining the present results with other works, it is suggested that the nodules nuc-leate in the local region where some of alloying elements are depleted.