To evaluate the physicochemical compatibility of rapidly solidified ribbons with transformer insulating fluids, isothermal heating process was carried out in order to prove the sustainability of these materials. Fe-based amorphous ribbons were immersed in mineral and vegetable transformer oils for a period of 580 h at 110 C and 140 C. Chemical analyses of oils after experimentation have shown absence of amorphous alloys' components such as Fe, Si, and B. In addition, a stability of magnetic properties is witnessed via the measurements of iron losses. Moreover, X-ray diffraction patterns of ribbons after aging experiments reveal a fully amorphous structure. Calculated lifetimes from accelerated aging test show a good stability of amorphous ribbons in field conditions.