The Fatigue Properties of Anodized Aluminum Alloys

Tuesday, May 6, 2025: 4:00 PM
Room 14 (Vancouver Convention Centre)
Ms. Ashley Kobylinski , Loyola Marymount University, Los Angeles, CA
Prof. Omar S. Es-Said , Loyola Marymount University, Los Angeles, CA
Dr. Michael Hahn , Northrop Grumman Corporation, Torrance, CA
Mr. Michael Niedzinski , Constellium LLC, Customer Application Engineering, Ravenswood, AL
Mr. Xaiodong Sun , Loyola Marymount University, Los Angeles, CA
Kade Cochran , Loyola Marymount University, Los Angeles, CA, Germany
Joey Slaybaugh , Loyola Marymount University, Los Angeles, WI
Sarah Leka , Loyola Marymount University, Los Angeles, CA
Dr. Ricky Whelchel , Constellium Aerospace and Transportation, Ravenswood, WV
Anodizing is applied on aluminum alloy surfaces to improve wear and corrosion resistance- specifically in aerospace applications. Despite these benefits, the anodized coating adversely affects the fatigue properties of the aluminum alloy. The fatigue life is dependent on the alloy and type of chromic or non-chromic anodizing.

The fatigue knockdown factors (KDF) of 7050-T7451, 2195-T8, and 2050-T8 prepared by as-received (no anodizing, control), chromic, boric-sulfuric, or tartaric-sulfuric anodizing are evaluated. The fatigue life of each alloy and anodize condition are compared to the corresponding alloy and as-received condition. The fatigue testing was conducted with a rotating-beam R.R. Moore machine at 30 ksi and 50 ksi. Results show that chromic anodizing improved fatigue life for Al-Li alloys. The chromic anodized specimens showed fatigue life improvement for 2195-T8 at 30 ksi (KDF=2.16/1.04) and 2050-T84 at 50 ksi (KDF=1.06), and better lives overall compared to boric-sulfuric and tartaric-sulfuric with KDFs of 0.37-0.80. Comparing experimental data and SEM images, decreased anodized layer thickness resulted in improved fatigue life. Chromic anodizing consistently had the thinnest layer with an average thickness of 1.19 µm. The high applied stress (50 ksi) had lower cycles to fracture, and fractured surfaces showed crack initiation and one origin. In contrast, the low applied stress (30 ksi) had greater cycles to fracture, greater variability in the number of cycles, and fractured surfaces showed crack nucleation with multiple origins.

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