Investigation of acceleration factor for pre-corrosion fatigue degradation: model and analysis

The acceleration corrosion factor (ACF) for accelerated corrosion test under service or natural exposed environment is the most important parameter in the accelerated corrosion test (ACT). The material property was degraded seriously in pre-corrosion environment, and the corrosion damage was characterized by fatigue strength. So, the acceleration factor was defined as the ratio of fatigue strength in different environments, and the expression was proposed in consideration of the degradation process of fatigue strength with corrosion time. To evaluate the fatigue property, the pre-corrosion fatigue life was assumed to follow the two-parameter Weibull distribution, the detail fatigue rating (DFR) method in pre-corrosion environment was proposed, and the relationship between the DFR and the corrosion time was expressed as an exponential function. The acceleration corrosion factor based on the DFR was proposed by comparing the degradation process in accelerated corrosive environment and the natural exposed environment, and was proved to be a constant regardless of corrosion time. Finally, the typical ACF of LY12CZ Aluminum alloy specimen was calculated.