Anion embedded sol-gel films on Al for corrosion protection

We report here on the successful incorporation of organic anions into a sol-gel film on Al as a means of enhancing the protection against corrosion. Following our previous study where we showed that hydrophobic sol-gel films provided pronounced corrosion inhibition, we studied the corrosion inhibition that phenylphosphonic acid (PPA) has when embedded inside a thin so]-gel coating oil Al. The anion of this organic anion tends to stay inside a phenyltrimethoxysilane (PTMOS) based sol-gel film due to pi-interactions. Our findings, which are derived primarily from potentiodynamic polarization measurements, electrochemical noise, scanning electron microscopy measurements and Auger-electron spectroscopy (AES), clearly show that the organic phosphonate adds to the protection efficiency of the sol-gel film. (C) 2004 Elsevier Ltd. All rights reserved.