Q:
What are Stress Corrosion Cracking
and Corrosion Fatigue?





A:
    STRESS CORROSION CRACKING:

  • Tensile stresses act in concert with corrosion.

  • Stresses can be external or residual.

  • Can result in catastrophic failure.

  • Intergranular or transgranular caracking
    can occur. Intergranular corrosion tendencies
    are good initiation points.

  • Austenitic SS and precipitation hardening
    Al alloys are prime candidates.


    CORROSION FATIGUE:

  • Fluctuating or cyclic stress imposed on
    corrosive environment produces fine to broad
    cracks with little or no branching.

  • Typically filled with corrosion product.

  • Stress concentrations are frequently present
    (pits, grooves). Transgranular is more common.

  • In less aggressive environments, "shot
    peening" helps to increase fatigue life.