Corrosion fatigue is caused by the joint action of cyclically applied stresses and a corrosive medium (generally aqueous). Metals will fail due to cyclic application of stress (fatigue). The presence of an aqueous corrosive environment causes such failure more rapidly. The frequency of the applied stress affects the rate of degradation in corrosion fatigue. Ordinary fatigue is generally not frequency dependent. Low-frequency applied stresses cause more rapid corrosion rates. Intuitively, low frequencies cause extended contact time between cracks and the corrosive medium. Generally, the cracks formed are transgranular.