Some aspects in designing passive alloys with an enhanced corrosion resistance

The technical and biomedical use of alloys containing reactive metals in aggressive environments is possible due to the spontaneous formation of thin oxide layers which slow down corrosion reactions by several orders of magnitude. Oxide films of important technical metals like Cr and Cu are cation semiconductors, and therefore they are electrochemically unstable and susceptible to anodic decomposition in the contact with electrolyte solutions. Alloying with elements that easily undergo oxidation and formation of highly charged cations, which interact electrostatically with the mobile cation vacancies, results in an enhanced electronic conductivity of their oxide films. This is an effective way how to design an alloy with significantly greater corrosion resistance in aggressive environments in comparison with its constitutive elements. The present paper describes several selected systems investigated under conditions of their real application. (c) 2008 Elsevier Ltd. All rights reserved.