Corrosion Fatigue

  Corrosion-fatigue is the result of the combined action of an alternating stress and a corrosive environment. The fatigue process is thought to cause rupture of the protective passive film, upon which corrosion is accelerated. The introduction of a corrosive environment often eliminates the normal "fatigue" limit of a ferrous alloy, thereby creating a finite life regardless of stress level.

The corrosive environment can cause a faster crack growth and/or crack growth at a lower tension level than in dry air. Even relatively mild corrosive atmospheres can reduce the fatigue strength of aluminum structures considerably, down to 75 to 25% of the fatigue strength in dry air. No metal is immune from some reduction of its resistance to cyclic stressing if the metal is in a corrosive environment. Control of corrosion fatigue can be accomplished by either lowering the cyclic stresses or by corrosion control.