Effects of minor elements on the polarization behaviors of Al-Zn-Mg alloy.

Abstract

Hardness and electrochemical polarization characteristics of Al-Zn-Mg alloys containing up to 0.1 at% of Cu, Cr, Si and Ti were investigated. The Vicker's hardness of the alloys aged at 180°C did not change remarkably by the addition of these contents up to 0.1 at%. Pitting potential of the alloys in 0.5N NaCI solution changes into noble value with increase in Cu and/or Cr contents. Passivation current density of the alloys reduces with increase in Cu, Cr and Ti contents. Pitting potential changes into noble value and passivation current density reduces with increasing aging time.These phenomena correspond to the change of solute quantity of Zn and/or Mg in the surface layer of the alloy materials.