Correlations between corrosion inhibition efficiencies and DFT calculated molecular parameters are critically evaluated for nine imidazole-based compounds on eight Cu/Zr materials in 3 wt% NaCl solution. To this end, 31 molecular parameters—such as ionization potential, electron affinity, and HOMO–LUMO gap—are considered and it is shown that one-parameter correlations either do not exist or have a limited success. For this reason, we present a simple method for building multiple regression models. Our analysis suggests that materials can be classified into two categories, depending on how useful molecular electronic parameters are as descriptors in QSAR models. We also point to the asymmetry of the inhibition efficiency metric that quantifies corrosion inhibitors and activators in a strikingly different way and to resolve the problem we introduce a symmetrized inhibition efficiency metric that treats inhibitors and activators equivalently.