Abstract The effect of thin coatings on the damage to brittle materials due to static and dynamic loading has been examined for hard carbon layers on germanium. For quasi-static ball indentations a significant increase in the load for ring-crack formation was observed. The increase depends strongly on the ratio of coating thickness to ball radius. The results are in good agreement with theoretical predictions. Examination of the impact damage caused by a high-velocity liquid jet showed only a small increase in rain-erosion resistance. Coating debonding, leading to a local loss of protection, was a serious problem.