Stress corrosion cracking crack fronts

Let us assume that the plastic deformation at the crack tip activates the metal, as in the previous model. If we are dealing with a non-noble metal and if the corrosion potential at the crack tip is relatively low, a corrosion reaction can take place that produces hydrogen by reduction of protons. The hydrogen that locally dissolves into the metal leads to embrittlement in the zone of maximum stress in front of the crack tip. 

---