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Influence of surface finishing on corrosion behaviour of Mg-Al hydrotalcite doped hybrid sol-gel coatings on Al alloy in saline environment

Abstract:

The behaviour of hybrid sol-gel coatings doped with hydrotalcite-like compound applied on AA2024-T3 alloy was investigated in the present work. The hybrid sol-gel coatings were prepared by copolymerization of 3-Glycydoxypropyltrimethoxysilane (GPTMS) and tetra-n-propoxyzirconium (TPOZ). Three different surface finishing on the aluminium alloy AA-2024-T3, grounded, chemical etching and degreased were studied. A sol-gel film with hydrotalcite 5% w/w was deposited by dip coating procedure. The presence of hydrotalcite particles was confirmed by means of X-ray diffraction technique. The different surface morphologies were characterised using mechanical profilometry. The corrosion resistance properties were studied by means of electrochemical impedance spectroscopy and salt fog spray cabinet. The results show higher barrier properties in grounded aluminium substrates. © (2010) Trans Tech Publications.