Study of a sol-gel process in the preparation of hybrid coatings for corrosion protection using FTIR and 1H NMR methods

The corrosion protection of aluminium alloys for use in transport industry requires new solutions due to the restriction of use of chromate coatings traditionally use for these purposes. One of the promising alternatives is the organic-inorganic hybrid materials (OIHMs). The formation of OIHMs by a two-step process from two separately prepared sols has been studied and intermediate products formed during synthesis characterized by in situ attenuated total reflectance FTIR and 1H NMR spectroscopy. Coatings were synthesized by alkoxide sol-gel reaction, using the organically modified siloxane precursors tetraethyl orthosilicate (TEOS) and 3-methacryloxypropyl trimethoxysilane (MAPTMS) (Sol 1), and zirconium tetrapropoxide (ZTP) chelated with methacrylic acid (MAA) (Sol 2). Oxoclusters were formed during chelation of ZTP with MAA. The double bond of MAA in a sol can further polymerize with itself or with the acrylic group of MAPTMS to form a polymerized chain during curing. The thermal cure protocol was improved by polymerization under daylight. Every step in the synthesis was shown, by in situ ATR FTIR and 1H NMR spectroscopy, to be important. Their good mechanical and chemical properties enable synthesized sols to be applied on various materials as coatings and used for corrosion protection of metals. The properties of coatings applied on aluminium alloy 7075-T6 were studied.