Anodization of aluminum alloys is a common means of providing corrosion protection. However, the anodization process can cause a reduction in the fatigue strength of the alloy. This problem is especially severe in aluminum-copper alloys. Fatigue strength losses of 41% were measured in this research for sulfuric acid anodized AA2219-T851 150 mm thick plate, when tested in rotary bending. Testing of a second heat of plate showed comparable behavior. The fatigue strength debit was attributed to pitting of the surface during anodization. Further investigation revealed that the pits were at sites originally occupied by the copper rich constituent particles that remain as artifacts of the casting process. Subsequent testing of sulfuric acid anodized 25 mm diameter AA2219-T8511 extrusion showed virtually no fatigue strength loss. In this case, no pits were observed at the fracture origins. An investigation of the microstructure revealed the cause for the difference in behavior for the two product forms. In the case of the thick plate, the Cu rich constituent particles were found to be large and connected, where as in the extrusion, the constituent particles were small and discontinuous. Given that the Cu rich constituent dissolves readily in the sulfuric acid electrolyte, the extent of damage is thus much greater for the case of large connected particles vs. small discontinuous particles. The microstructural differences are most likely attributable to the differing extent of working experienced between thick plate and small diameter extrusion, where in the latter, extensive work has broken down the original cast microstructure more effectively. This work was subsequently extended to the less copper rich AA2024 alloy. Testing of 165 mm diameter AA2024-T851 bar showed a fatigue strength loss of 29 % following sulfuric acid anodizing vs. 12 % for 19 mm bar. Again, the microstructure revealed larger and more connected Cu rich constituent in the large cross section product form.