Materials Performance

AUG 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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19 MATERIALS PERFORMANCE: VOL. 57, NO. 8 AUGUST 2018 Information on corrosion control and prevention An aerial view of retired military planes at Davis-Monthan Air Force Base. U.S. Navy photo by Mass Communication Specialist 3rd Class Amber Porter Desert Dryness Preserves Aircraft T he 309th Aerospace Maintenance and Regeneration Group (309 A M ARG) at the Davis-Monthan Air Force Base (Tucson, Arizona, USA), commonly known as "The Boneyard," is probably one of the strangest airf ields in the world. It's here that the U.S. Air Force, Nav y-Marine Corps, Army, Coast Guard, and several federal agencies (including NASA) store their obsolete, unwanted, excess, and out-of-service aircraft. With more than 4,400 aircraft, 309 A M ARG is the largest storage and preservation facility of this ty pe in the world. Because there is little humidity in the air, the desert climate in Tucson is not conducive to corrosion, which makes it an ideal location to preserve the stockpiled aircraft. The chief mission of the 309 A M ARG is to supply the Air Force with spare parts. Parts from The Boneyard can make the difference between an aircraft being grounded or operational. When an air- craft arrives at the 309 A M ARG, weapons and classif ied hardware are removed. It is then thoroughly washed, which is espe- cially important for marine aircraft or those employed in tropical locations. Fuel is f lushed and mechanical parts are pro- tected with a lightweight oil. Canopies are sealed with a white vinyl latex coating to prevent them from becoming crazed and cracked, and to protect the cockpit interior from heat. Joints are sealed to keep out dust. Once this is done, the air- craft is towed to its storage area. The hard soil at the airf ield is strong enough to support the weight of a 300-metric ton aircraft, which makes it easy to move aircraft without the need for pavement. Most importantly, however, the airf ield 's climate and clean air mini- mize corrosion and degradation. The atmosphere here has a very low average humidity of 38%, so moisture contact 1 9 4 3 – 2 0 1 8 NACE INTERNATIONAL 75 (time-of-wetness) is minimal. Tucson is hundreds of kilometers away from a marine environment and corrosive sea salt, the hot climate has no snow (so deic- ing salt is not used), and there is no pollu- tion from heav y industry. As a result, the corrosion rates are very low. Carbon steel corrosion rates in Phoenix, Arizona, which has an environment similar to Tucson, are reported to be ~5 μ m/y, which is near the benign end of ISO Corrosivity Category C2-Low. 1 Aircraft have been stored at this air- f ield since the end of the World War II, when the storage facility was established at Davis–Monthan Air Force Base for B-29 and C-47 aircraft because of Tucson's low humidity, infrequent rainfall, alkaline soil, and high altitude (2,550 ft [777 m])— all factors that help to reduce rust and corrosion. 2 The inventory now includes F-15 and F-16 f ighters, Hercules and Galaxy transports, A-10 attack planes, B-1 nuclear bombers, Harrier jump jets, experimental aircraft, helicopters, and missiles. A lthough the 309 A M ARG is commonly perceived as an aircraft grave- yard, a sizable percentage of the aircraft stored here will f ly again. About 10% are kept in good condition in case they need to be deployed in the future by the United States or its allies. Some are used as tar- get drones. More information can be found in the online f ilm, "The Boneyard," by Jeff Watson. References 1 BS EN ISO 12944-2:2017, "Paints and Var- nishes. Corrosion Protection of Steel Struc- tures by Protective Paint Systems. Classifica- tion of Environments" (London, UK: BSI, 2017). 2 "309th Aerospace Maintenance and Regen- eration Group," Wikipedia , The Free En - cyclopedia, https://en.wikipedia.org/wiki/ 3 0 9 t h _ A e r o s p a c e _ M a i n t e n a n c e _ a n d _ Regeneration_Group ( July 9, 2018). Source: NACE International member Robert A. Francis, Ashburton, Victoria , Australia—email: Robfrancis766@gmail . com.

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