Reliable metallization schemes for chemical vapor deposited diamond are critical for expanding the use of diamond components in electronics and optics. We present here the results of our investigation of several metallization schemes produced by cathodic are deposition. The deposition process also allows the control of the metal ion energy, and this is used to promote good adhesion between film and substrate. Films of Mo, Cu, Ta and W with thickness varying between 50 and 1000 nm were deposited on free-standing smooth diamond substrates and annealed at temperatures between 200 degrees C and 900 degrees C. Interdiffusion and solid state reactions between carbon and the deposited metal were studied using backscattering spectrometry and X-ray diffraction. Of the films tested, W was the only one virtually unaffected by annealing at all temperatures. Upon annealing at 200 degrees C all metal films remained intact and did not delaminate.