  Hard disk drives (HDDs) are used as secondary storage in a number of digital
electronic devices owing to low cost ($<$0.1\$/GB at 2016 prices) and large
data storage capacity (10TB with a 3.5 inch HDD). Due to the exponentially
increasing amount of data, there is a need to increase areal storage densities
beyond$\sim$1Tb/in$^2$. This requires the thickness of carbon overcoats (COCs)
to be$<$2nm. Friction, wear, corrosion, and thermal stability are critical
concerns$<$2nm, where most of the protective properties of current COCs are
lost. This limits current technology and restricts COC integration with heat
assisted magnetic recording technology (HAMR), since this also requires laser
irradiation stability. Here we show that graphene-based overcoats can overcome
all these limitations. 2-4 layers of graphene enable two-fold reduction in
friction and provide better corrosion and wear than state-of-the-art COCs. A
single graphene layer is enough to reduce corrosion$\sim$2.5 times. We also
show that graphene can withstand HAMR conditions. Thus, graphene-based
overcoats can enable ultrahigh areal density HDDs$>$10Tb/in$^2$.
