Observations on the Early Stages of Corrosion on AA2099-T83

Abstract

An Al–Cu–Li aerospace alloy has been investigated to determine the order in which corrosion at different types of sites occurs in AA2099-T83. Specifically, the sequence of galvanic attack on intermetallic (IM) particles and other sites of AA2099-T83 was determined as a function of time, in 0.1 M NaCl, through the use of scanning electron microscopy and electron backscatter diffraction characterization techniques. The earliest attack occurred at isolated grains and grain boundaries and on Li-containing dispersoids. Similarly, some constituent IM particles showed evidence of trenching in the surrounding alloy matrix. These IM particles included Al7Cu2Fe and another group of unidentified particles which displayed complete trenching within the first 10 min of exposure. Al13(Fe, Mn)4 were next most active followed by Al37Fe12Cu2 with Al6(Fe,Mn) and large TiB2 particles being the least active.

TSA anodising voltage effects on the near-surface coarse intermetallic particles in the AA2024-T3 and AA2198-T8 alloys

“…In the last years, many works were carried out in order to understand the corrosion mechanism and the corrosion resistance of the AA2024 alloy [18][19][20][21][22][23][24][25][26][27][28]12] and also of the Al-Cu-Li alloys [4,11,[29][30][31][32][33][34][35][36][37]. Recently, some researchers reported the effect of microstructure on the corrosion initiation in Al-Cu and Al-Cu-Li alloys [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. All these works demonstrated the higher susceptibility of these alloys to localised corrosion and the need for corrosion protection.…”

Change in Oxygen Reduction Reactivity of Intermetallics: A Mechanism of the Difference in Trenching around Al–Fe and Al–Fe–Si Particles on AA1050 in NaCl

“…Fe is an unavoidable impurity in Al alloys, and exhibits very low solubility in Al; therefore, commercial Al alloys always contain Ferich IMPs such as Al-Fe, Al-Fe-Si, and Al-Fe-Mn. 7,13,14,17,[28][29][30][31] Another unavoidable impurity is Si. Therefore, the role of Si in Ferich IMPs during pit initiation needs to be determined.…”