Corrosion inhibition of Al 6061 T6/Al2 O3p 10% (v/v) composite in 3.5% NaCl solution with addition of cerium (III) chloride

The effect of cerium on 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 conducted at different inhibitor agent concentrations (0, 200, 1000 and 2000 ppm of cerium) and for exposure times ranging from 2 h to 30 days. Corrosion inhibition power evaluation and surface layer characterization have been carried out by electrochemical (polarization potentiodynamic curves and impedance measurements) and free corrosion tests followed by several instrumental analyses (optical microscopy, x-ray photoelectron spectroscopy, scanning electron microscopy). Electrochemical data have shown that cerium compounds offer a noticeable inhibition level against localized corrosion in all considered cases and that the maximum protective power against corrosion attack is evident when the inhibitor is added at a 200 ppm concentration. 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 without homogeneous distribution. This behaviour decreased the protection power of the passive layer while increasing composite substrate corrosion tendency. Copyright (C) 2002 John Wiley Sons, Ltd.