Size-dependent role of S phase in pitting initiation of 2024Al alloy

Size-dependent electrochemical role of the S phase at the initial corrosion stage of 2024Al alloy has been elucidated by transmission electron microscopy technique. A critical size of about 10 nm is identified below which S phases are out of electrochemical function at the initial corrosion stage, when Al20Cu2Mn3 dispersoids play a crucial role. The electrochemical function of S phases becomes remarkable and triggers the local dissolution of the Al matrix with increasing the size. Moreover, the mechanism of the size effect has been discussed in detail. (C) 2016 Elsevier Ltd. All rights reserved.