In this paper, the diffusion behavior of hydrogenated amorphous carbon into Co-Pt-TiO2 and Ruthenium films was first investigated. Impact of carbon on Co-Pt-TiO2 composite film and its diffusion in Co-Pt-TiO2 and ruthenium films were studied using Time-of-Flight Secondary Ion Mass Spectroscopy. Magnetic coercivity drop was observed for Co-Pt-TiO2 films coated with ruthenium and carbon hybrid overcoat at varied thickness ratio. Co-Pt-TiO2 film is widely used in perpendicular magnetic recording. Carbon depth profile showed that carbon readily diffuses in Co-Pt-TiO2 film because of its porous structure. However, carbon diffusion in ruthenium film is limited even annealing up to 200 degrees C in argon. Carbon's diffusion length and coefficient in Co-Pt-TiO2 are much higher than that in Ru film. The activation energy was calculated for both cases.