Materials Performance

MAY 2015

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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21 NACE INTERNATIONAL: VOL. 54, NO. 5 MATERIALS PERFORMANCE MAY 2015 Information on corrosion control and prevention Ray Gamache (left) and Mike Roland test polyurea coatings on pieces of AAV steel armor. Photo: U.S. Naval Research Laboratory/Jamie Hartman. The U.S. Naval Research Laboratory accelerated corrosion on pieces of AAV armor in heated aquariums flled with seawater. Photo: U.S. Naval Research Laboratory/Kathleen Galligan. —Kathy Riggs Larsen permanent damage when the load is re- moved, which makes it multi-hit capable. "In conventional materials, you can have something that's really stiff but doesn't stretch much; or you can have something really soft, like Silly Putty, and it stretches a lot," says Roland. "Poly ureas, they can stretch to 10 times their original length, but the force it takes to do that is enor- mous—so you get toughness, the best of both worlds." To demonstrate how poly urea pro- tects armor from corrosion, Roland and Gamache exposed steel test pieces to salt water in their lab. "We wanted to simulate what happens in the f ield, so we bent some of the test pieces," says Roland. In addition to f lat test pieces, the research- ers used pieces with a gentle bend and a 90-degree acute bend. They tested f ive coatings: two ty pes of paint, a poly urea used by NR L in other armor applications, and two poly ureas developed by a private company. "We set up aquarium tanks f illed with seawater. We raised the tem- perature to 40 and 50 centigrade [104 and 122 °F] just to accelerate the corrosion, and we bubbled air so there was plenty of oxygen." He notes that if the coated pieces were tested just as f lat plate, they would all work; but the paints tended to crack on the bent pieces. "The poly ureas don't [crack] because they're elastomeric, rub- bery so they stretch and don't open up a pathway for the water," he comments. NR L is also monitoring samples in actual seawater troughs at its Key West, Florida facility. "The ones that performed the best in salt water tanks in the lab are per- forming best at Key West," Roland adds. This research project could help ex- tend the life of today's A AVs and may also guide the next generation of ship-to-shore connectors. "We solved the corrosion problem," says Roland. "And with a negli- gible increase in weight, we also provided a higher payload capacity and the poten- tial for better ballistic protection." While a long-term corrosion solution is important, the USMC also needs to know how to best maintain the A AVs currently in use. "We quantified how much they're going to lose in ballistic performance with the corrosion," says Roland. This will guide the Marine Corps in determining when they need to replace or repair the armor, which will save money, he notes. "Innovative sustainment concepts, like those NRL is investigating, enable us to avoid the cost of new design, development, and production of new components," says Tim Bergland of the USMC Advanced Amphibious Assault (A A A) office. Source: U.S. Naval Research Laboratory, Contact Kyra Wiens—e-mail: Reference 1 U.S . Marin e s, O p eratin g Forc e s, AAV-7, equipment/vehicles/aav-7 (April 2, 2015).

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