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The aluminium alloys of the series 5xxx or 7xxx are prone to a heterogeneous
precipitation along the grain boundaries which results in a heterogeneous
hydrogen embrittlement. The presence of H weakens the interface along the
precipitates while the ‘natural’ ligaments remain safe. We first analyse the
decohesion process of such heterogeneous grain boundary and try to get insight
on the peak for the corrosion observed for precipitates about 50nm long. We then
define an ‘average’ cohesive model that mimics the influence of the hydrogen
along a homogenised grain boundary with a decrease of cohesion energy with the
concentration of H. A 2D polycrystal exhibiting intergranular failure is considered
and loaded under mode I to analyse the condition for slow crack growth. We
investigate how the presence of initial stresses issued from a predeformation are
necessary for crack propagation. Monotonic, fatigue and applied constant loads
are considered.