The fracture photos point to stress raisers from holes, brackets or other drillings. Corrosion played no part whatever in this one.
That is one hell of a reach to decide whether you see trans granular cracking vs intergranular cracking in that 1 X photo.
Corrosion can occur anyplace, especially in drilled holes after- production where the surface may have a course texture. Of course I would not care to extrapolate from a internet photo. However the two different sides of the hole do appear to have two different types of fatigue initiations at their surface which in my view could possibly consider abusive machining or corrosion on one side and secondary initiation on the other.