Corrosion Protection of Aluminum Alloy AA7020 in NaCl Solution by Hybrid Sol–Gel Coatings

Abstract

In this study, two different hybrid sols as tetraethyl orthosilicate/(3-Glycidyloxypropyl) trimethoxysilane (TEOS/GPTMS) and tetrapropyl orthotitanate/(3-Glycidyloxypropyl) trimethoxysilane (TPOT/GPTMS) were prepared and Aluminum AA7020 alloy was coated with these sols by the dip-coating method. Corrosion behavior of coated samples in 3.5% NaCl solution was investigated using potentiodynamic polarization (Tp) and electrochemical impedance spectroscopy (EIS) methods. The same electrochemical test and analysis procedures were applied to an uncoated AA7020 sample in order to the investigate corrosion protective perfomance of TEOS/GPTMS and TPOT/GPTMS coatings in 3.5% NaCl solution. Morphological analyses of the coated and uncoated AA7020 samples were made before and after corrosion test measurements via Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectrometry (EDS). The results obtained from EIS and Tp measurements for the coated and uncoated specimens were reviewed for the corrosion protection activities of the sol–gels coating. TEOS/GPTMS and TPOT/GPTMS sol–gel coatings were found to have high protection effect for the corrosion of AA7020 alloy in a 3.5% NaCl medium.