Enhancement corrosion resistance of (3-glycidoxylpropyl)-silsesquioxane hybrid films and its validation by gas-molecule diffusion coefficients using MD simulation

Based on silsesquioxanes (SSO) derived from hydrolytic condensation of (γ-glycidoxylpropyl) trimethoxysilane (GPMS) and tetraethoxysilane (TEOS), two hybrid films, f-GPMS-TEOS-SSO (f-GTS) modified with 10 wt-% TEOS and f-GTS modified with 50 wt-% DGEBA (f-GTSD), were prepared. The anticorrosion properties (corrosion potential, Ecorr, and corrosion current density, I _corr) of the bare aluminum alloy (AA) and the two films on AA were tested by electrochemical measurements with typical potentiodynamic polarization curves. The I_corr values of three samples were significantly different with the order of f-GTSD>f-GTS>AA, which implies that the DGEBA addition in the f-GTSD coating indeed enhances the electrochemical corrosion resistance. Two different 3D-amorphous cubic unit cells, cell(f-GTS) and cell(f-GTSD), as models were employed to investigate self-diffusion coefficients by MD simulation for the NO₂, _SO2 and H2O molecules. All the three self-diffusion coefficients of NO₂, SO₂ and H₂O diffusing in cell(f-GTSD) were less than the coefficients in cell(f-GTS), which validates the corresponding anticorrosion-experiment results. Two reasons that the addition of DGEBA in the system of f-GTS lead to the decrease of the gas self-diffusion coefficient compared to the f-GTS system were discussed.