Search

Intergranular corrosion defects formed after a 24 h immersion in a 1 M NaCl solution in a 2024-T351 Al alloy were characterized using a combination of electron microscopy techniques. Results showed the dissolution of intergranular Cu-rich precipitates all along the corroded grain boundaries. Cu species were incorporated inside the amorphous alumina oxide film identified in the corroded grain boundaries leading to the formation of structural defects in the oxide film. A 10–200 nm-thin metallic Cu-rich layer was also observed at the oxide/metal interface and at the tip of the intergranular corrosion defect. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • H did not influence the elementary processes of intergranular corrosion. • H had a significant impact on the local reactivity of 2024 aluminium alloy. • In the presence of H, the number of corroded interfaces strongly increased. • H led to embrittlement of subgrain boundaries and CSL grain boundaries. • H-induced changes led to a ramification of intergranular corrosion defects. 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. [ABSTRACT FROM AUTHOR]

This paper provides a new insight into the understanding of the susceptibility to intergranular corrosion (IGC) of 2024 Al alloy. Whatever the exposure conditions, coincidence site lattice high-angle grain boundaries (CSL HAGBs) slightly contributed to IGC damage because of their low contribution to the cumulative length of GBs. Low-angle grain boundaries (LAGBs) showed intrinsic susceptibility to corrosion initiation almost similar to random HAGBs and lower susceptibility to IGC propagation. However, cyclic corrosion tests promoted both corrosion initiation and propagation at LAGBs. This was mostly due to the trapping of corrosion-induced hydrogen in the core of the dislocations defining the LAGBs. [Display omitted] • Low contribution of CSL grain boundaries to intergranular corrosion (IGC). • Lower susceptibility to IGC propagation for low-angle grain boundaries (LAGBs). • Cyclic corrosion tests promoted corrosion initiation and propagation at LAGBs. • Trapping of hydrogen in the core of the dislocations defining the LAGBs. • Significant influence of hydrogen on corrosion initiation and propagation. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of a 2050 aluminium alloy was studied in a NaCl solution. The structure of precipitation did not fully explain the susceptibility to intergranular (in the -T34 state) and intragranular corrosion for the aged state (the -T8 state). A relationship between the nature of interfaces, the grains characteristics (size, internal misorientation and orientation according to the plane exposed to the electrolyte) on one hand and the corrosion susceptibility of the alloy on the other hand was clearly established. Galvanic coupling between grains with different internal misorientations helped to explain the intergranular corrosion susceptibility of the -T34 state. [ABSTRACT FROM AUTHOR]

Highlights: [•] After natural ageing, intergranular corrosion was observed for the 2050 alloy. [•] After artificial ageing at 155°C, transgranular corrosion was observed. [•] The corrosion behavior of alloy 2050 depended on the distribution of T1 precipitates. [•] Cyclic corrosion tests induced subgrain boundary dissolution. [•] Hydrogen trapping at T1 precipitates was evidenced for artificially aged 2050 alloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] The corrosion behaviour of the 2050 Al–Cu–Li alloy was studied. [•] Its corrosion behaviour was linked to the distribution of T 1 precipitates. [•] The copper content in solid solution also influenced its corrosion behaviour. [•] In the T34 metallurgical state, the alloy was susceptible to intergranular corrosion. [•] During ageing at 155°C, the alloy became susceptible to intragranular corrosion. [ABSTRACT FROM AUTHOR]

Highlights: [•] The corrosion behaviour of the nugget of a FSW (Al–Cu–Li alloy) joint was studied. [•] A post-welding heat treatment modified the corrosion behaviour of the nugget. [•] For the nugget, intergranular/intragranular corrosion was linked to T 1 precipitation. [•] A gradient in the nugget grain size led to galvanic coupling at a mesoscopic scale. [•] Onion rings structure explained the localisation of the corrosion in parallel bands. [Copyright &y& Elsevier]

Abstract: This work is focused on the role of hydrogen in corrosion damage induced by the cyclic exposure of 2024 aluminium alloy to chloride media with air emersion periods at room and/or negative temperatures. Various analysis and microscopic observation techniques were applied at intergranular corrosion defects. A mechanism involving the contribution of hydrogen to the degradation of the alloy mechanical properties is presented. Several consecutive stress states appear during cycling, resulting from volume expansion of the electrolyte trapped in the intergranular defects during emersion phases at −20°C. These stress states lead to hydrogen diffusion, transport and trapping. [Copyright &y& Elsevier]