[en] The chemical erosion of C, TiB₂, and TiC by reaction with H has been studied from 420 to 1540 K using H pressures characteristic of fusion devices. For graphite, erosion yields range from 2.0 x 10^-4 to 7.4 x 10^-4 C/H over this temperature range. A change in the gas phase product distribution is observed as a function of temperature and reaction time. Methane is most abundant at low temperatures and short reaction times, while C₂ and C₃ species increase in abundance at higher temperatures and after extended reaction times. For C-rich TiC, initial behavior is similar to graphite, but the time evolution of gas phase products differs. TiB₂ shows no evidence of reaction below 1300 K and lower erosion yields than graphite at higher temperatures. The superior erosion resistance of TiB₂ suggests that it may be a better candidate material than graphite for fusion applications requiring refractory low-Z materials