An electrochemical study on the passivity of age hardened Al–Mg–Si alloy

Abstract

The objective of the present study is to investigate the effect of ageing heat treatment condition on the structural characteristics and corrosion protection performance of the passive layers forming on the surface of age hardened Al 6061 alloy using X-ray diffraction, Mott-Schottky, point defect model and potentiodynamic polarization techniques. The results showed that n-type semi-conductive passive layers are formed on the surface of age hardened samples; creation of more lattice microstrain in the alloy (as a result of age hardening process) leads to the formation of passive layers including less crystal defects giving them less passive current density values. Moreover, the point defect model results showed that crystal defects will diffuse at higher rates through more defective passive layers giving the age hardened alloy less resistance to the pitting corrosion.