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

摘要

In the first part of this work,based on sils-esquioxanes(SSO)derived from hydrolytic condensation of(3-methacryloxypropyl)trimethoxysilane(MPMS)and tetraethoxysilane(TEOS),two hybrid films,f-MPMS-SSO(f-MS)and f-MPMS-TEOS-SSO(f-MTS)modified with 15 wt% TEOS,were prepared.The anticorrosion properties(corrosion potential,E_(corr),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 are significantly different with the order of f-MTS < f-MS < AA which implies that the TEOS addition in the f-MTS coating indeed enhances the electrochemical corrosion resistance.Correlations between the structures of two films and anticorrosion properties were discussed.In the second part of this work,two different 3D-amorphous cubic unit cells,cell(f-MS)and cell(f-MTS),as models were employed to investigate self-diffusion coefficients by molecular dynamics(MD)simulation for the NO2,SO2 and H2O molecules.All three self-diffusion coefficients of NO2,SO2 and H2O diffusing in cell(f-MTS)were less than the coefficients in cell(f-MS),which validates the corresponding anticorrosion-experiment results.Two reasons why the addition of TEOS in the system of f-MTS leads to a lowering of the gas self-diffusion coefficient compared to the f-MS system,were discussed.