Effect of electroless Ni-P plating on rotary bending fatigue strength of A2017-T4 aluminum alloy

In this study, A2017-T4 aluminum alloy was plated with electroless Ni-P with different phosphorus content and rotary bending fatigue test was conducted to investigate the effect of hydrogen by plating on fatigue properties. The fatigue strength of the low-phosphorus type Ni-P plated specimen was higher than that of the untreated specimen, while that of the high-phosphorus type plated specimen was much lower. It is clear that the fatigue strength differs greatly depending on the phosphorus content in the plating film. The decrease in fatigue strength of the high phosphorus type plating specimen was attributed to hydrogen induced by plating from hydrogen analysis. Thus, despite the previous report that 2000 series aluminum alloys do not exhibit hydrogen embrittlement in slow strain rate tensile tests under wet condition, it was found that A2017-T4 aluminum alloy undergo hydrogen embrittlement when the alloy is plated with high-phosphorus type electroless Ni-P and fatigue-tested on rotary bending machine.