Corrosion Resistance of Precipitation-Hardened Al Alloys: A Comparison between New Generation Al-Cu-Li and Conventional Alloys

Abstract

The corrosion resistance of conventional (AA2024-T3, AA6082-T6 and AA7050-T7451) and the new generation (AA2050-T84, AA2098-T351, AA2198-T8, and AA2198-T851) precipitation-hardened alloys has been studied and compared using electrochemical and non-electrochemical approaches. The AA6082-T6 was the most resistant alloy followed by the new generation Al-Cu-Li alloys, except the AA2050-T84. All the alloys exhibited pseudo-passivity, except for the AA2024-T3 alloy which presented the highest number of pitting sites per cm 2 and also exhibited the most insidious form of corrosion amongst the alloys tested. However, the alloy with the highest corrosion depth was the AA2050-T84 alloy followed by the AA2024-T3 and AA7050-T7451 alloys. Intergranular corrosion was associated with rapid rates of penetration. In addition to the microstructural features of the alloys before corrosion, the modes of localized corrosion in the alloys were also influenced by evolving microstructural features (such as re-deposited Cu) during corrosion.

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

“…The anodisation of the intermetallics resulted in the formation of micrometric sized cavities on the anodic film [82] Al-Cu-Fe H 2 SO 4 It was observed some imperfections (cavity) on the surface due to the local dissolution of the particles [83] Taking into consideration that many works reported the importance of comparing the mechanical [94][95][96][97] and corrosion [24,43,[98][99][100] properties of the AA2024 alloys with that of the Al-Cu-Li alloys, the behaviour of the coarse particles in the AA2024-T3 Al-Cu-Mg alloy during anodising was also evaluated and reported. The results presented are helpful for the development of novel surface treatments for the optimal performance of these aluminium alloys in service.…”

“…Taking into consideration that many works reported the importance of comparing the mechanical [94–97] and corrosion [24,43,98 100] properties of the AA2024 alloys with that of the Al-Cu-Li alloys, the behaviour of the coarse particles in the AA2024-T3 Al-Cu-Mg alloy during anodising was also evaluated and reported. The results presented are helpful for the development of novel surface treatments for the optimal performance of these aluminium alloys in service.…”

An assessment of pitting corrosion in anodized aluminum alloys: It might not be what it seems

“…For the anodized condition in aerated media and in the presence of chloride ions (Cl − ), it was possible to observe the “pseudo‐passive” region, whereas for Al alloys in the bare condition, the passive region can only be observed in deaerated media or in aerated media containing Cl − ions. [ 18 ] The increase in time until passive film breakdown depends on the thickness of the anodic layer, the electrolyte used for anodizing, and the defects in the film, as shown in Figure 2e–g. It is important to highlight that the anodic layer might be highly defective, as was the case of one of the tested samples (curve 4).…”

“…It is important to point out that to analyze the depth and extension of the corrosive attack on Al alloys, different methodologies have been used and reported in the literature, such as optical microscopy (OM) and optical profilometry (OP) from the surface and analysis by OP and scanning electron microscopy (SEM) in metallographic cross-sections. However, some works have shown that the results obtained by OP can lead to misinterpretations, [18][19][20][21][22][23][24][25][26][27][28][29] once that, by this technique the calculation of the surface profile is carried out from the distortion of a regular shape light pattern projected on the surface. [26] Therefore, different results can be obtained depending on the condition of the surface such as accumulation of corrosion product or even depth limitation.…”

Correlating corrosion modes with the microstructure of the 2XXX series alloys: A comparative approach

“…corrosion [5][6][7][8][9] that affects the aesthetics of parts and, more crucially, the integrity of structures that are subjected to fatigue and/or static stresses and then can result in catastrophic failures, 10,11 especially when these alloys are used in wing and/or fuselage structures.…”