Breakdown of passivity of aluminium alloys by intermetallic phases in neutral chloride solution

Aluminium alloys are successfully used in several technological application s. Aluminium itself has weak mechanical properties, hence it is alloyed wit h other elements and thermally treated to improve and tailor its characteri stics. These processes remarkably change the original structure of Al from a homogeneous solid solution to a complex polyphase structure. The growth o f intermetallics in the Al matrix allows the hardening process to take plac e but a modification of the chemical resistance of the alloy can occur. In this paper the influence of intermetallics, formed in some binary and terna ry alloys (Al-Cu, Al-Cu-Be, Al-Mg-Zn), on the passivity breakdown and corro sion properties of aluminium is investigated and discussed with the aid of electrochemical measurements (anodic polarisation, electrochemical impedanc e spectroscopy EIS) and surface analysis (SEM, TEM, AES). (C) 2000 Elsevier Science Ltd. All rights reserved.