Alumina Scale Formation: A New Perspective



This article is corrected by:

  1. Errata: Erratum to “Alumina Scale Formation: A New Perspective” Volume 94, Issue 8, 2698, Article first published online: 9 August 2011

  • M. Rühle—contributing editor

†Author to whom correspondence should be addressed. e-mail:


Oxidation of Al2O3 scale-forming alloys is of immense technological significance and has been a subject of much scientific inquiry for decades. The oxidation reaction is remarkably complex, involving issues of alloy composition, kinetics, thermodynamics, microstructure, mechanics and mechanical properties, crystallography, etc. A brief overview of the formation of passivating, thermally grown oxide Al2O3 scales will be given in the light of recent findings on the defect structure and associated transport behavior of α-Al2O3. It is inferred that the electronic structure of Al2O3 is of direct relevance to understand the Al2O3 scale growth. We also discuss the effect of the so-called “reactive” elements (REs)—Y, Zr, and Hf—on reducing the rate of Al2O3 scale thickening by reducing the outward flux of aluminum. An important aspect of the “new perspective” is the suggestion that the REs change the electronic structure of Al2O3—the relevant near-band-edge defect (grain boundary) states that are crucial to vacancy creation both at the scale/gas and scale/metal interfaces.