We show for the first time that both chemical corrosion and electrochemical corrosion of silicon-based films does occur, and that this corrosion leads to device failure. Chemical corrosion is the dominate failure mechanism when devices are aged between 500 and 1500 h. Typically, a small number of failures are found as a result of chemical corrosion. However, if the devices are improperly packaged, then this mechanism can be responsible for most if not all failures. The mechanism is characterized by an activation energy between 0.6 and 1.0 eV depending on the passivation stoichiometry. Electrochemical corrosion dominates long term failure and is strongly dependent upon the resistivity of the passivation. We found that the median lifetime could vary by two orders of magnitude depending on the film resistivity. Because of this large variation in median lifetimes, it is important to characterize the resistivity of the passivation films used for given technologies, remembering, of course, that the resistivity is strongly dependent on film stoichiometry, applied field, and local geometry.