Influenza della concentrazione del cerio sull'inibizione alla corrosione di un materiale composito a base di alluminio

The effect of cerium concentration on the corrosion inhibition of Al 6061T6 /Al2O3p 10% (v/v) metal matrix composite, in aerated 3.5% NaCl solution after different immersion times at room temperature and pressure was investigated. The evaluation of the corrosion inhibition power and the surface layer characterization has been carried out by electrochemical and free corrosion tests following by several instrumental analysis. In particular, the morphological analysis, carried out by means of OM and AFM, has highlighted some important results: -when Ce is present in solution at low concentration, a homogeneous passive layer, consisting of Al and Ce oxides, growson the composite forming a high protective film owing to the synergic effect of these compounds; -when Ce is present in solution at high concentration the process oxidation of the inhibitor becomes competitive with Al oxidation. This lead to high Ce oxidation and precipitation with a contemporary decreasing of Al oxidation. Such behaviour produces a non homogeneous surface layer, formed by different zones, some rich in Ce oxides and some other poor in Ce oxides with a defective Al oxide film. These last areas could become preferential sites of localized corrosion attacks.