Zinc injection has been widely applied for corrosion resistance of nuclear materials. The mechanism of the corrosion resistance, however, has not been completely understood. The protocol improvement is not possible without such information. In the present research, the effects of zinc on corrosion of SS 304 induced by H$_2$O$_2$ were studied at ambient pressure and temperatures up to 80$^o$C using a custom-made flow setup. Zinc ion in the form of zinc acetate at different concentrations was injected into the flow system composed of a glass hot cell where the SS 304 specimens were fully immersed in H$_2$O$_2$ solutions. XRD, XRF and SEM-EDX were used to examine the chemical composition and surface morphology of the specimens. The results indicated that pitting was the dominant form of corrosion found under the experimental conditions. Zinc ions tend to help mitigate corrosion of the material via playing a significant role in oxide formation on the steel surface.