Enhanced corrosion protection of aluminum by ultrasonically dip coated sodium silicate thin films

A simple ultrasonic dip-coating process was utilized to fabricate sodium silicate thin films on aluminum alloy substrates, and their chemical and corrosion properties were investigated as a function of their concentration in the solution. The attenuated total reflectance Fourier transmission infrared spectroscopy (ATR-FTIR) and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Na, Si, and O in the films. The polarization resistance (Rp) of the as-received aluminum substrates was found to be 10 ± 2 kΩ·cm2 in 3.5 wt% NaCl solutions. In comparison, sodium silicate thin films prepared from 1 M solution exhibited a large Rp of 593 ± 32 kΩ·cm2. The corrosion protection efficiency was calculated from the corrosion current, which was found to be 99.52%. This study shows that sodium silicate thin films can be used as a protective coating against corrosion to aluminum substrates under aqueous NaCl environments.