Influence of hydrogen on the propagation of intergranular corrosion defects in 2024 aluminium alloy

Abstract

To study the influence of hydrogen on the intergranular corrosion mechanism of a 2024 aluminium alloy, samples were hydrogen precharged by cathodic polarisation and then exposed to a NaCl solution. EBSD analyses and SEM observations showed that hydrogen increased the number of corroded interfaces and led to the embrittlement of low-angle grain boundaries which were not susceptible to corrosion without hydrogen precharging. The increase of the reactivity of the 2024 aluminium alloy in the presence of hydrogen gave a new insight into the intergranular corrosion mechanism: corrosion-induced hydrogen promoted the intergranular corrosion propagation and partially controlled the corrosion defect morphology.

When all intermetallics dealloy in AA2024-T3: Quantifying early stage intermetallic corrosion kinetics under immersion

“…Regardless of the mechanism leading to local IM corrosion, the inevitable result is the formation of corrosion pits due to either dissolution of the particle (dealloying) or cathodic undermining (trenching) with consequent particle detachment (etch out) [23][24][25]. Further propagation of corrosion pits underneath the surface can in turn lead to intergranular attack of the grain boundaries and the nucleation of corrosion cracks [26][27][28][29][30][31][32]. Corrosion pits can therefore act as stress concentrators and reduce the load bearing capacity of the structure in question, eventually resulting in dramatic failures.…”

Stress Corrosion Cracking Behavior of Fine-Grained Al5083 Alloys Processed by Equal-Channel Angular Pressing (ECAP)

“…For the as-received and deformed samples, the potential difference in GBPs was found to be higher than the matrix difference. GBPs form more galvanic microcells, leading to a higher amount of microgalvanic corrosion [53][54][55]. As can be seen in Figure 6, the initial microstructure showed fine precipitates homogeneously distributed in the sample.…”

“…Liao et al [53] reported that the copper corrosion rate increases as the thin electrolyte layer (TEL) thickness decreases during the initial stages. Researchers studying the influence of hydrogen on the propagation of intergranular corrosion (IGC) defects of 2024 aluminum alloy concluded that H did not influence the elementary processes of IGC, although it had a significant impact on the local reactivity [54]. In addition to these factors, the evolved hydrogen seems to play a very important role in the degradation of the materials [34,35,55].…”

Intergranular corrosion in evolving media: Experiment and modeling by cellular automata

“…The preferential attack of these grain boundaries results in a specific corrosion mode named intergranular corrosion (IGC). Challenges relative to intergranular corrosion concern various materials such as nickel based alloys [1][2][3], aluminum based alloys [4][5][6] or steels [7][8][9]. One specific issue is about IGC of nonsensitized stainless steels (SSs) in nitric acid.…”