Corrosion fatigue is fatigue in a corrosive environment. It is the mechanical degradation of a material under the joint action of corrosion and cyclic loading. Nearly all engineering structures experience some form of alternating stress, and are exposed to harmful environments during their service life. The environment plays a significant role in the fatigue of high-strength structural materials like steel, aluminum alloys and titanium alloys. Materials with high specific strength are being developed to meet the requirements of advancing technology. However,their usefulness depends to a large extent on the extent to which they resist corrosion fatigue. The effects of corrosive environments on the fatigue behavior of metals were studied as early as 1930. The phenomenon should not be confused with stress corrosion cracking, where corrosion (such as pitting) leads to the development of brittle cracks, growth and failure. The only requirement for corrosion fatigue is that the sample be under tensile stress.