The aim of this research was to establish the effects of superphosphate fertilizer on the fatigue life of 2024 = T4 aluminium alloy. Rotating beam, direct stress and reverse bend fatigue tests were carried out on both notched and un=notched specimens. The results showed that moist superphosphate caused a dramatic loss in fatigue life even at stresses as low as 4 tons/sq.in. It was found that the type of fracture obtained in air was the same for all stress systems studied, but that the cycle frequency and the presence of a stress concentrator such as a notch modified the type of fracture produced in air tests. The presence of the corrodent profoundly modified the shape of the fracture and valley fractures were produced with all the stress systems studied.

Research studies included the effect of superphosphate on fatigue crack initiation and propagation and it was found that although the corrodent had a marked effect on the crack propagation rates, it had little, if any, effect on the crack initiation. From these studies a tentative theory of corrosion accelerated fatigue has been postulated. This theory has been used to explain the results obtained in the present research.