Effects of Surface Treatment on Fatigue Property of A5052-H14 and A2017-T4 Aluminum Alloys

In this study, the effect of anodization and electroless Ni-P plating on the fatigue strength of commercial A5052-H14 and A2017-T4 aluminum alloys was investigated. The coated aluminum alloys were tested using a rotary bending fatigue testing machine. Anodization led to a slight increase in the fatigue strength of the A2017-T4 alloy of approximately 10% because of the suppression of the generation of fatigue crack, and anodization with a 5-µm thickness for A5052-H14 also led to a slight increase in the fatigue strength. However, anodization with a 20-µm thickness for A5052-H14 led to reduced fatigue strength because of the pits that formed in the film. In addition, electroless Ni-P plating drastically improved the fatigue strength of the A5052-H14 alloy by suppressing the generation of fatigue crack．It also improved the fatigue strength of the A2017-T4 alloy in the high-stress region. However, the fatigue strength in the low-stress region was the same as that of the non-coated specimens．This fatigue strength should have originated from the hydrogen embrittlement by the hydrogen introduced into the specimen during the plating.