Hydrogen effects during IGSCC of pure Al-5Mg alloy in NaCl media

The conditions to propagate an intergranular stress corrosion crack in pure, precipitate-free, Al-5Mg alloy in 30 g/l NaCl have been determined. SCC tests are performed on specimens with a thin notch which favours single cracking and solution confinement. Slow strain rate tests in a simulated confined medium without oxygen are used to simulate the natural confinement. They show that the main cathodic reaction during SCC is the reduction of hydrogen. Reversible grain boundary embrittlement is obtained by localised hydrogen pre-charging. The role of hydrogen during intergranular stress corrosion cracking is therefore established, in close relation with localised dissolution.