Effect of La Surface Coatings on Oxidation Behavior of Aluminum Alloy/SiCp Composites A. Pardo,* M. C. Merino,* R. Arrabal,* and S. Feliu´ Jr  Received June 9, 2006; revised October 27, 2006 The oxidation behavior of aluminum-matrix-composites (A3 xx.x/SiCp) has been studied after La deposition with conversion and electrolytic treatments. Kinetics data of the corrosion process were obtained from gravimetric tests performed at different temperatures (350, 425 and 500°C). The nature of the corrosion products and the influence of the microstructure on the morphology and growth of the oxidation layer were analyzed by scanning-electron and atomic-force microscopy, X-ray photoelectron spectroscopy and X-ray dif- fraction. The extent of oxidation degradation in untreated composites was characterized by a phenomenon of oxidation preferentially localized in matrix/ SiCp interfaces favoring MgO formation. La coatings favored a homogeneous oxidation of the composite surface favoring MgAl 2 O 4 spinel formation. In addition, this oxide increased the surface hardness of materials. KEY WORDS: oxidation; aluminum–matrix composites; lanthanum; coatings. INTRODUCTION Al–Si casting alloys reinforced with SiC particles (SiCp) have found many applications in aerospace, transportation and industrial sectors since they *Departamento de Ciencia de Materiales, Facultad de Ciencias Quı´micas, Universidad Complutense, 28040, Madrid, Spain; e-mail: anpardo@quim.ucm.es  Centro Nacional de Investigaciones Metalu´rgicas CSIC, Avda. Gregorio del Amo 8, 28040, Madrid, Spain. Oxidation of Metals, Vol. 67, Nos. 1/2, February 2007 (Ó 2007) DOI 10.1007/s11085-006-9045-7 0030-770X/07/0200-0067/0 Ó 2007 Springer Science+Business Media, LLC 67