Corrosion fatigue describes a situation where a metal is exposed to both mechanical fatigue and corrosion simultaneously.
Corrosion generally involves the degradation of an exposed metal surface. Corrosion occurs in various forms ranging from uniform attacks over the entire surface to severe local attacks. Pure mechanical fatigue describes a condition where a material can fail as a result of a cyclical load far below the ultimate tensile strength.
If the metal is exposed to both a corrosive environment and mechanical fatigue simultaneously, the failure can take place at an even lower stress level and after a shorter time. Contrary to pure mechanical fatigue, there is no fatigue limit in corrosion-assisted fatigue.