Anion embedded sol–gel films on Al for corrosion protection

Abstract 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 sol–gel coating on Al. The anion of this organic anion tends to stay inside a phenyltrimethoxysilane (PTMOS) based sol–gel film due to π-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.