A steel structure experiences a cyclic load. The loading is parallel to the gravity direction, and the maximum and minimum loads are $40\%$ and $15\%$ of the steel yield strength, respectively. After $2$ years of service, the component is fractured, with a typical fatigue cracking feature observed under scanning electron microscopy.

Please indicate

$($A$)$ the direction of the crack initiation; $($B$)$ the direction of the crack propagation;

$($C$)$ the direction of the final shear lip of the component.

If the steel structure as mentioned above fractured in a corrosive environment under the same loading condition, how does corrosion affect stages in $($A$),($B$)$ and $($C$)?$