QSAR Model Construction and EFM Validation of Pyrimidine-Based Green Inhibitors for Copper Corrosion in 3.5 wt.% NaCl Solution

Quantitative structure-activity relationship (QSAR) model combined with electrochemical frequency modulation (EFM) was applied to develop and validate a predictive framework for pyrimidine-based green inhibitors of copper corrosion in 3.5 wt.% NaCl solution. Eight newly synthesized pyrimidine derivatives (PYR1-PYR8) were first tested experimentally by EFM at concentrations from 1 to 5 ppm and used as the training set for model generation. Their inhibition efficiencies increased with concentration, while the clear differences in performance among the compounds provided a solid basis for correlating molecular structure with anticorrosion behavior. Using genetic function approximation (GFA), the QSAR model linked inhibition efficiency to key molecular descriptors, including total energy, binding energy, frontier molecular orbital parameters, dipole moment components, molecular area, and molecular volume. To examine the model’s predictive ability, two additional derivatives from the same series, MDT and MDP, were selected as external validation compounds. Their inhibition efficiencies were first predicted from the QSAR equation and then verified experimentally by EFM under identical conditions. The results confirmed the predicted trend, showing that both compounds were effective inhibitors, with MDP performing better than MDT. At 5 ppm, MDT and MDP reached inhibition efficiencies of 89.68% and 99.29%, respectively, confirming the model’s usefulness for screening corrosion inhibitors