The chemical erosion of carbon was investigated in the linear plasma device Pilot-PSI for ITER divertor relevant hydrogen plasma flux densities 10 23 < Γ < 1025 m-2 s-1. The erosion was analyzed in situ by optical emission spectroscopy and post mortem by surface profilometry. The experiments indicate a threshold for the absolute carbon erosion rate as a function of plasma temperature Te around 0.7 eV, a peak of the surface temperature around 550 °C, and no dependence on plasma flux density. The latter implies a flux dependence of the chemical erosion yield as Γ-1. The value of the chemical erosion yield at the surface temperature of maximum erosion and Γ = 1 × 1024 m-2 s-1 was 0.9% for Te < 0.5 eV as determined by surface profilometry.