Abstract
In order to clarify the influences of HF gas on the low cycle corrosion fatigue strength and static corrosion velocity of 2014-T6 aluminum alloy, low cycle corrosion fatigue tests and static corrosion tests were conducted in a {HF gas (3ppm)+humid air (80°C, 70% relative humidity)} environment by using a laboratory made gas corrosion fatigue testing apparatus. The fatigue strength at 105 cycles in the {HF gas (3ppm)+humid air (80°C, 70% relative humidity)} environment was about 56% lower than that in air at room temperature. Corrosion pits were observed at the crack initiation region and brittle striation was predominant at the crack propagation region. The maximum corrosion velocity in the {HF gas (3ppm)+humid air (80°C, 70% relative humidity)} environment was 2×10-3mm/year. A tough fluoride film was formed on the surface of specimens due to the reaction of aluminum with humid HF. It can be considered that the static corrosion velocity was extremely low because the tough fluoride film prevented the further reaction of the fresh surface of aluminum with humid HF. However, the fluoride film was destroyed by repeated stress, and corrosion pits were initiated at the surface of low cycle corrosion fatigue test specimens influenced by the humid HF gas environment. These corrosion pits accelerated the initiation of corrosion fatigue cracks, which caused an extreme reduction in the corrosion fatigue strength of 2014-T6 aluminum alloy.
