Influence of tartaric-sulfuric acid anodic film on four-point bending fatigue behavior of AA 7050-T7451 samples

Tartaric–sulfuric acid (TSA) anodizing is an electrochemical process used for generating an anodic layer on the surface of aluminum alloys for aerospace applications. It must provide corrosion resistance and ensure no detrimental effect on the required fatigue properties for structural applications. This work aimed at analyzing the properties of the anodic layer and evaluating its influence on the fatigue behavior of the AA 7050-T7451. The film properties were analyzed using optical and scanning electron microscopies. The surface residual stress (SRS) field in the as-machined and anodized conditions was evaluated by the X-ray diffraction technique. The results showed that TSA induces an appreciable reduction in the fatigue life, especially at lower values of stress amplitude, due to the presence of defects at the interface between the substrate and the anodic film. No correlation was observed between the presence of the anodic layer and the development of a tensile SRS field.