We present results on nanoindentation and scratch testing on magnetic recording tape heads coated with sub-20 nm amorphous carbon layers, prepared by filtered cathodic deposition and plasma enhanced chemical vapour deposition. The hardness values of the coated devices are higher than that of the sputtered Al2O3 substrate. The coatings do not reduce friction but improve the scratch resistance of the tape heads. Hardness, which shows some correlation with scratch resistance is a contributing factor, especially at high load where it reduces plastic ploughing of the substrate. For low scratching load, the wear seems to be influenced by the adhesive properties of the film/substrate interface. Smoother surfaces and smaller tip radius should improve the accuracy of the results. This could provide better insight into the failure mechanism of these ultra-thin overcoats.