Alkaline etching and desmutting of aluminium alloy: The behaviour of Mg2Si particles

In the present study, the behaviour of coarse constituent Mg2Si particles during alkaline etching and desmutting of AA5052 aluminium alloy is investigated by monitoring the morphological and compositional evolution of the particles using quasi in-situ electron microscopy. An etching product film, consisting of Mg(OH)(2), and SiO2 center dot xH(2)O sublayers, is formed on particle surface during alkaline etching, which renders the particles inert. During desmutting in nitric acid, the etching product film is dissolved and dealloying of Mg occurs rapidly, resulting in Si-rich remnant. However, the population density of Si-rich remnant on alloy surface is similar to that of the initial Mg2Si particles. (C) 2020 The Authors. Published by Elsevier B.V.