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Journal of Applied Electrochemistry

, Volume 22, Issue 6, pp 541–552 | Cite as

Influence of the heat treatment in the electrochemical corrosion of Al-Zn-Mg alloys

  • P. L. Cabot
  • F. Centellas
  • J. A. Garrido
  • R. M. Rogríguez
  • E. Brillas
  • E. Pérez
  • A. V. Benedetti
  • P. T. A. Sumodjo
Papers

Abstract

The localized corrosion of Al-(5.03%)Zn-(1.67%)Mg-(0.23%)Cu alloys and high purity Al has been studied using electrochemical techniques, optical microscopy, SEM and EDX. The samples were previously submitted to different heat treatments in which coherent and incoherent MgZn2 precipitates with different distribution and aggregation degree were produced. The influence of NaCl and Na2SO4, dissolved oxygen, immersion time and convection were studied. In NaCl solutions, pitting potentials for the alloys were more negative than for aluminium, indicating an increase in their susceptibility to localized corrosion. Moreover, annealed and cold-rolled alloys presented more negative pitting and repassivation potentials than those submitted to age hardening with direct or interrupted quenching. In annealed and cold-rolled samples, pit nucleation and propagation takes place in the zones where MgZn2 is accumulated. In the case of the age-hardened alloys, a double pitting behaviour is observed, the first one in the magnesium and zinc enriched regions and the second in the matrix. While the cold water quenched alloy is susceptible to stress corrosion craking, the alloy submitted to the interrupted quenching process is less susceptible to intergranular attack. The sulphate ion shifts the pitting potential of aluminium and the alloys by chloride towards more positive values because it impedes local accumulations of the latter.

Keywords

Heat Treatment Dissolve Oxygen Na2SO4 Stress Corrosion Immersion Time 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman & Hall 1992

Authors and Affiliations

  • P. L. Cabot
    • 1
  • F. Centellas
    • 1
  • J. A. Garrido
    • 1
  • R. M. Rogríguez
    • 1
  • E. Brillas
    • 1
  • E. Pérez
    • 1
  • A. V. Benedetti
    • 2
  • P. T. A. Sumodjo
    • 3
  1. 1.Departament de Química Física, Facultat de QuímicaUniversitat de BarcelonaBarcelonaSpain
  2. 2.Departamento de Fisicoquímica, Instituto de QuímicaUNESPAraraquaraBrazil
  3. 3.Departamento de Química Fundamental, Instituto de QuímicaUSPSão PauloBrazil

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