Thin films of rare earlh transition metal (RETM) alloys are considered to be promising as media for high-density data storage in magneto-optic (MO) devices. These alloys, however, degrade rapidly through oxidation and corrosion due to the high reactivity of the RE metal. The addition of alloying elements could increase the intrinsic stability of the MO media [1,2]. Generally, two types of alloying elements have been considered: (1) an active metal (such as aluminum, titanium, chromium) or (2) a noble metal (such as platinum or gold). Although such alloying additions could improve the corrosion resistance, the exact mechanism of protection is not clearly understood. In this paper, we report the effects of Zr (active element) and Pt (noble element) on the oxidation behavior of FeTbCo MO films. Efforts were made to get a better understanding of the protection mechanisms provided by these two types of elements by using x-ray photoelectron spectroscopy (XPS).