The vibrational lifetime of the CN stretching mode has been measured at a Pt(111), polycrystalline Au and polycrystalline Ag electrochemical interface with sum-frequency generation (SFG). The lifetimes on Pt(111) and Au are potential dependent and range from 3 to 8 ps and 10 to 19 ps, respectively, with the longer lifetimes occurring at more positive potentials. Results for the Ag surface show solvent dependent lifetimes of approximate to 28 ps in a 0.1 M solution of NaClO4 in H2O and approximate to 60 ps when the solvent is changed to D2O. The results on all of these metals are surprising because of the comparatively short (1.5-3.0 ps) lifetimes predicted and measured for isoelectronic CO. The lifetimes on Ag are remarkable because of their similarity to those of freely-solvated CN- ions. We discuss our results in the context of a charge transfer to the substrate and also consider an image dipole mechanism.