Corrosion of AA2024-T3 Part III: Propagation

Optical and electron microscopes and EBSD were used to study the early stages of corrosion propagation during stable pit formation on AA2024-T3 Polished AA2024-T3 developed large scale rings of corrosion product typically a few hundred microns in diameter within 2 h of exposure to 0 1 M NaCl at room temperature These features were sectioned using diamond ultramicrotomy and substantial subsurface attack in the form of intergranular corrosion was observed beneath these sites with virtually no grain etchout A model is proposed for the mechanism of stable pit progression which involves extensive gram boundary attack followed by grain etchout leading to open pit formation Crown Copyright (C) 2010 Published by Elsevier Ltd All rights reserved