CHEMICAL STRUCTURE AND CURE KINETICS OF ENVIRONMENTALLY FRIENDLY CORROSION RESISTANT HYBRID NANOCOMPOSITE COATINGS

摘要

Environmentally friendly sol-gel nanocomposite coatings have been processed and characterized for corrosion protection of aerospace alloy AA2024-T3. The hybrid nanocomposite coatings were processed in solution using acid-catalyzed hydrolysis and condensation of precursors Glycidoxypropyl trimethoxysilane (GPTMS) and Tetramethoxysilane (TMOS) to form self assembled nanoscale composite. The product of condensation reaction was cured with a mono-amino silane and di-amino silane curing agents, respectively, via a one step and a two step process. Nanometer scale montmorillonite clay, Cloisite 15A was also dispersed in the precursor solution prior to chemical cross-linking and coating formation. The structure and composition of the hybrid coatings were determined by Fourier Transform Infrared Spectroscopy, (FTIR) and X-ray Diffraction Spectrometry (XRD). The hydrolysis and condensation kinetics were studied by using FTIR and a semi-quantitative equation was developed. The XRD results indicate a physical structure that is mostly amorphous with selective crystalline regions due to siloxane bridge formations. The Cloisite 15A clay dispersed in the coating was exfoliated, as shown by the disappearance of clay peak associated with d001.