Salt-nanoparticle systems incorporated into sol-gel coatings for corrosion protection of AZ91 magnesium alloy

Abstract

Sol-gel coatings were prepared from mixing tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) and then applied on the pre-treated AZ91 magnesium alloy by using the dip coating technique. The formation and morphological characteristics of the coatings were analyzed by using Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Three salts were incorporated into the coatings, and their corrosion inhibition performance was investigated by using electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. The results indicate that the addition of sodium gluconate (NaC6H11O7), potassium hypophosphite (KH2PO2), and manganese (II) acetate (Mn(CH3CO2)2) as inhibitors with a concentration of 0.1, 0.5, and 0.1 wt%, respectively to the coatings can enhance corrosion resistance. It was also found that the inhibition performance of the salt-containing coatings is highly improved when 0.5 wt% of cloisite 20A nanoparticle as the surface modifier is added to the coating.