We consider a thin layer of an incompressible viscous Newtonian fluid coating the inner wall of a horizontal cylinder rotating with constant speed. Assuming the film height is small compared to the radius of the cylinder, we formally derive a closed equation for the height h(t, θ) > 0 of the liquid film by means of a lubrication approximation: ht + hθ + γ h3(hθθθ + hθ) θ = g h3 cos θ θ in (0, T ) × T This rimming flow equation is of fourth-order, degenerate-parabolic, and quasilinear. Compet- ing effects are observed between viscosity, the surface tension γ, and gravity g. For g = 0 and a fixed mass m, the two-dimensional manifold M(m) := m + a sin θ + b cos θ a2 + b2 < m2 is invariant. If 0 < g ∼ δ ≪ 1 is small, we show that solutions which are bounded away from zero converge exponentially fast to a δ-neighbourhood of M(m). Here, the existence of solutions on a large time scale t ∼ 1/δ2 can be shown. Moreover, such solutions evolve on two distinct time scales: On the fast time scale t they only rotate around the origin with the speed of the cylinder, while on the slow time scale τ = δ2t the dynamics are governed by an ODE in τ on M(m).