C6F12O (heptafluoroisopropyl pentafluoroethyl ketone) has been considered as a potential eco-friendly gas insulating medium to replace SF6, the most potent greenhouse gas, used in medium-voltage equipment. In this paper, we explored the compatibility between the C6F12O-air gas mixture and metals such as copper and aluminum to evaluate the long-term behavior of the new gas. Aging tests for the C6F12O-air gas mixture and metal were conducted, and the composition as well as the microstructure was analyzed. It was found that the interaction between C6F12O-air and copper results in the decomposition of C6F12O and corrosion of copper. Several by-products including CO2, C3F6, C4F8O, and C6F12 can be detected. Obvious color modifications and corrosion points exist after interaction. The compatibility between C6F12O-air and aluminum is superior to that between C6F12O-air and copper. Their interaction did not lead to the corrosion of aluminum. As for engineering applications, anticorrosion measures should be taken on copper to avoid the occurrence of negative chemical interactions.