Potentiodynamic study of the corrosion protection of aluminium by plasma-polymerized coatings

The corrosion-protective performance of plasma-polymerized (PP) coatings on aluminium substrates has been investigated by potentiodynamic (cathodic) polarization curve measurement, X-ray photoelectron spectroscopy (XPS) and temperature-programmed photoelectron emission (TPPE) measurement. PP films from tetraethoxysilane (TEOS)/O2, hexamethyldisiloxane/O2 and cyclohexane were deposited on previously argon plasma treated aluminium substrates by a 13.56 MHz radiofrequency generator. The weight loss rate obtained from the cathodic polarization curve for the PP film samples utilized as the working electrode was employed to evaluate the corrosion-protective performance. The PP films of TEOS/O2 mixtures gave the best protective performance. The corrosion potential for all the PP films became more negative than that for the substrate only. The XPS analysis indicated that TEOS films have a chemical structure like SiO2. The TPPE analysis revealed that the argon plasma pretreatment of the metal substrate enhances greatly the ability of the surface to emit electrons.