What Does Fatigue Corrosion Mean?
Fatigue corrosion is corrosion caused by fatigue of materials. It refers to the fatigue fracture of a metal aggravated by a corrosive environment or stress corrosion cracking (SCC) of a metal aggravated by cyclic stress. It is a special case of stress corrosion cracking in that it combines a corrosion process and applied stress on the materials.
Fatigue corrosion is similar to SCC, except that the stresses are cyclic and it can occur in any environment.
Fatigue corrosion is generally transgranular and does not show branching, which is characteristic of SCC.
Corrosionpedia Explains Fatigue Corrosion
Fatigue corrosion is the reduced ability of a metal to withstand repeated stress when exposed to the combined action of stress and a corrosive environment as compared to the effects of stress alone. It causes a fracture surface similar to ordinary fatigue except that in some cases corrosion products are present in the outer sections of the cracks.
Fatigue corrosion can occur on many different types of metal products, ranging from heavy equipment to the metal panels used in construction and shipbuilding. Materials that would have the ability to repassivate during a static loading are very vulnerable to the repetition of oxide film breakdown.
Fatigue corrosion is caused by crack development under the simultaneous action of corrosion and cyclic stress. As in the case of stress corrosion cracking, fatigue corrosion is dependent on factors including:
Fatigue corrosion can be prevented through reducing:
- Fatigue, by minimizing vibration and pressure fluctuation
- Corrosion, by using high-performance alloys resistant to corrosion fatigue
- Corrosion, by using coatings and inhibitors to delay the initiation of corrosion fatigue cracks
Although there is no direct relationship between the sensitivity to corrosion fatigue and the mechanical properties of the material, high-strength alloys tend to be most highly prone. In normal fatigue, the frequency of the stress cycles is not important. But in fatigue corrosion, low-cycle stresses are more damaging than high-frequency stresses.