Corrosion inhibition of Al 6061 T6/Al2O3p 10% (v/v) Composite in 3.5% nacl Solution with Addition of Cerium (III) Chloride

The effect of cerium on the corrosion inhibition of Al 6061 T6/Al2O3p 10% (v/v) metal matrix composite, in aerated 3.5% NaCl solution after different immersion times at room temperature and pressure was investigated. Experimental tests were effected at different concentration of the inhibitor agent (0, 200, 1000, 2000 ppm of cerium) and for exposure times ranging from 2 hours to 30 days. The evaluation of the corrosion inhibition power and the surface layer characterization has been carried out by electrochemical (polarization potentiodynamic curves and impedance measurements) and free corrosion tests following by several instrumental analysis (Optical Microscopy – OM, X-ray Photoelectron Spectroscopy – XPS, Scanning Electron Microscopy – SEM). Electrochemical data have showed that cerium compounds, in general, offer a noticeable level of inhibition against localized corrosion in all cases considered. This effect is more evident when the concentration of the added inhibitor is of 200 ppm. Surface analysis revealed chemical and morphological characteristics of the passive layer. In particular, a higher amount of inhibitor led to the formation of a surface film with a higher content of cerium but with a distribution in a non homogeneous form. This behaviour decreased the protection efficiency of the passive layer increasing the corrosion of the composite substrate.