Improvement of Corrosion Resistance of Organic - inorganic Hybrid Coatings Based on Epoxy - silica via Aromatic Diol Curing Agent

• Published in: ʻUlūm va tiknūlūzhī-i pulīmar Vol. 17; no. 6; pp. 359 - 367
• Main Authors: Zand, R Zandi, Langaroudi, A Ershad, Rahimi, A
• Format: Journal Article
• Language: Persian
• Published: 01.02.2005
• ISSN: 1016-3255

Organic-inorganic hybrid coatings prepared by sol-gel process due to having organic - inorganic networks in their structure have a set of mechanical and chemical properties and as a result they attract a lot of interest. These coatings were prepared by a two-step process: hydrolysis and condensation reaction of silane compounds, that is, 3-glycidoxy propyl trimethoxy silane (GPTMS) and tetramethoxysilane(TMOS) in the presence of acid catalyst and as a bisphenol A(BPA) and an aromatic diol. Surface investigation of films and the bonds between the epoxy functional group of silane compound and the curing agent and also cross - linking between them and the curing agent and oxide layer' were carried out by optical microscopy images and ATR-IR spectroscopy. Corrosion resistance of these coatings was studied by electrochemical and accelerated corrosion(salt spray)experiments. Both optical microscopy and ATR-IR spectroscopy observations revealed that the surface of these coatings have not any crack and reduction of absorption peaks in the region of 750 and 906 cm-1 and the presence of a peak at 936 cm-1 were attributed to cross - linking between BPA and epoxy function of silane compound and oxide layer of metal support surface, respectively. Electrochemical and accelerated corrosion experiment results showed that these compounds have good corrosion resistance. Study of the effect of H2O and silane content on the degree of corrosion resistance by electrochemical experiments indicated that the completion of hydrolysis reaction and reduction of silane content (% TMOS) make improvement on corrosion resistance of organic - inorganic hybrid coatings. (Al substrate.)