Preparation and Anti-corrosion Properties of Silica Aerogel-modified Polyurethane Composite Coatings
Waterborne polyurethane(WPU)coating,a new kind of green material due to its excellent wear resistance,flexibility,low-temperature resistance and chemical medium resistance,has been widely attached attention to the field of marine corrosion protection.In this paper,hydrophilic modification of the hydrophobic silica(SiO2)aerogel was carried out by urea aldehyde modification.Then,the unmodified-and modified-SiO2 aerogels as filler were added into the WPU coatings with doses 0.5％,1％and 2％,re-spectively,aiming to improve the anti-corrosion properties of WPU coatings.The functional groups and microstructure of SiO2 aerogel were characterized by Fourier transform infrared spectroscopy(FTIR)and scanning electron microscopy(SEM).These results proved that SiO2 aerogel was successfully modified by urea-formaldehyde.The anti-corrosion properties of coatings with different fillers were studied by con-tact angle test,electrochemical impedance spectroscopy(EIS),adhesion test and salt spray test.The re-sults showed that the adhesion of the coating was significantly improved after adding hydrophilic-modi-fied SiO2 aerogel.When 1％hydrophilic modified SiO2 aerogel was added,the adhesion of the composite coating was improved by 36％correspondingly,the low-frequency impedance modulus of the composite coating increased above 6 × 107 Ω·cm2 after immersion in 3.5％NaCl solution for 70 d.There was no ob-vious bubbling phenomenon on the surface of the composite coating with 1％hydrophilic modified SiO2 aerogel after the 480 h salt spray testing,which showed its best anti-corrosion performance.Thus,it is concluded that the hydrophilic modification of the hydrophobic SiO2 aerogel by the urea aldehyde modifi-cation can improve the dispersibility of the hydrophobic SiO2 aerogel in the WPU coating,the interface compatibility with the coating and the barrier and shielding effect of the SiO2 aerogel on corrosive ions.Furthermore,the corrosion resistance of the WPU coating is improved.
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