SCC evaluation of a 2297 Al-Li alloy rolled plate using the slow-strain rate technique

The stress corrosion cracking (SCC) susceptibility of 2297 Al-Li alloy in 1 M NaCl + 0.01 M H₂O₂ solution (CP solution) and 1 M NaCl + 0.01 M H₂O₂ + 0.6 M Na₂SO₄ solution (CPS solution) was investigated by slow-strain rate tests at various strain rates ranging from 10^?5 s^?1 to 10^?7 s^?1. The roles of H₂O₂ and SO₄^2? in the corrosion process were estimated by potentiodynamic polarization and electrochemical impedance spectroscopy. 2297 Al-Li alloy does not fracture ascribed to SCC in CP solution, while it undergoes SCC in CPS solution. In CPS solution, with a decreasing strain rate from 10^?5 s^?1 to 10^?7 s^?1, the SCC susceptibility firstly rises and then declines exhibiting a peak value at a strain rate of 10^?6 s^?1. H₂O₂ promotes the active dissolution while SO₄^2? lowers the corrosion rate. The SCC fracture is associated with a decline in the dissolution rate of the crack tip by SO₄^2?, which leads to stress concentration. In CPS solution, a reduction in the local dissolution rate of the crack tip leads to stress concentration, resulting in SCC fracture. As the preferred initiation site for a crack, pits also show a noteworthy effect on SCC of 2297 Al-Li alloy.