Thermodynamic calculation and experimental investigation of the surface enrichment of electrochemically activated Al–Me (Sn, In, Zn) alloys

• Published in: Electrochimica acta Vol. 50; no. 13; pp. 2629 - 2637
• Main Authors: Andreev, Yu.Ya, Goncharov, A.V.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 30.04.2005; Elsevier
• Subjects: Activation; Alloying metals; Aluminum; Sulphate; Surface enrichment; Sulphate; Activation; Aluminum; Surface enrichment; Alloying metals
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2004.11.022

The formula for surface composition of solid solution Al–Me (Zn, Sn, In) has been derived from the Gibbs's adsorption equation. Using the first-principles data of Al and Me surface energies, the values of adsorption x Me, and surface enrichment of alloy x Me/ N Me versus concentration in the bulk of alloy N Me, were calculated. The value of x Me/ N Me decreases in the order In–Sn–Zn in Al–Me alloy. The surface of Al–1 wt.% Sn alloy was analyzed with SIMS and Auger methods for Al and Sn both prior and post corrosion attack or anodic dissolution in Na 2SO 4. The maximum experimental magnitude of x Sn/ N Sn = 136 was found to be close to the theoretical one. A large diffusion zone was revealed in the near-surface layer of that alloy. The phenomena of ultra-high rate of atomic diffusion within surface layer at room temperature and high solubility of tin are discussed in terms of thermodynamic vacancy model.