Previously published results on plasma treatment of semi-noble metal surfaces [2] or Cu [1] have suggested the plasma-induced transformation of predominantly sp3C (binding energy ∼285 eV [5]) to either sp2 or carbidic carbon (binding energies of ∼284.5 eV or near 283 eV, respectively), but this issue—including the resistance of the transformed layer to further plasma-induced carbon removal—has not been specifically addressed. The findings presented here indicate that plasma-induced transformation of C is observed for Co and Cu metal surfaces under a variety of plasma chemistries and conditions. These findings indicate that plasma-induced transformation of sp3C to graphite or carbidic carbon is specific to metallic surfaces, and that upon transformation, these layers are extremely resistant to further removal by non-oxidizing plasma treatment. The presence of such residual layers can be problematic for many applications, including subsequent metallization [4].