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It's A Boat, It's A Tank … The Marine Corps EFV is Both - page 2 / 3





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Pacheco explained that the Marine Corps needs to continue to develop and employ a complementary mix of capabilities that can initiate amphibious operations from over the horizon, go where the enemy is not, seamlessly transition from sea to land, collapse enemy anti-access defenses, and close the shore in order to rapidly build up combat or soft power at the objective. "The EFV will be the primary means of tactical mobility for the Marine rifle squad during the conduct of amphibious operations ashore," he added.

Controlling and Preventing Corrosion

The AAV7A1's slow water speed was not its only drawback. The vehicle also was prone to corrosion caused by water entrapment, primarily in the vicinity of its Enhanced Appliqué Armor Kit. Specific problem areas, which have all been remedied over the years, include:

The rubber used in the armor kit’s vulcanization process was porous and absorbed water, resulting in corrosion. The Marines corrected this problem by replacing the rubber with a low-moisture absorbent material. The paint process used on exterior surfaces was inadequate for handing the demands of a marine environment. The paint process was modified to use inorganic zinc primer, which provides a salt spray resistance of more than 5,000 hours. The crevices around inserts for mounting bolts and the edges of the laminated armor kit plates trapped moisture, allowing corrosion to form that resulted in severe delamination of the armor and loss of material. The crevices and plate edges have been sealed with polysulfide sealant to eliminate the entrance and trapping of moisture.

Subra Bettadapur, lead engineer for Materials and Corrosion Prevention for the EFV Program, said the new vehicle integrates design changes that will avoid water entrapment. In addition, he noted that the vehicle's "robust production ready-paint system" contains significantly improved corrosion- resistant chemicals, primers, and paint. He added, "Continued effort is being made to prevent dissimilar metals usage, and where not possible, provide adequate protection to prevent corrosion."

Compared to its precursor, the EFV also will use more titanium and stainless steel for structural components. Other corrosion-resistant materials, including aluminum alloys, also are being used to protect against oxidation, reduce

weight, and improve ballistic properties.

"With regard to the welding process, friction stir welding, which has the potential for providing joint designs with superior strength, fatigue, and

An Expeditionary Fighting Vehicle moves at high- water speed while undergoing cold-weather testing in Alaska's Prince William Sound. Photo courtesy of EFV Program Office.

ballistic properties, but more significantly improved corrosion mitigation, is being developed specifically for EFV hull structures and is planned to be utilized for future EFV build," said Battadapur. "Also vehicle inspection, maintenance, and corrosion repair plans, and training methods, with repair kits, have been developed, and are being utilized to monitor and control in order to achieve significant corrosion prevention and control capability in the EFV."

Battadapur added that the EFV will boast impressive environmental credentials. It will not use conventional hexavalent pretreatment and paint primers and topcoats, which are carcinogenic. "Extensive testing of the pretreatment chemicals and paint primers and paints was performed, and aerospace-quality chemicals and methods were selected," he recalled. Three of the coatings selected include NAVAIR-developed trivalent chromium pretreatment, the corrosion preventive compound Navguard, and highly corrosion-resistant non-hexavalent primer and topcoat.

"In addition, titanium inserts were coated with a ceramic coating and used," Battadapur said. "Also, significantly superior Electro Magnetic Interference seals and method of sealing, and conductive paint were used. "Water traps were eliminated through the use of improved seal materials and proper sealing techniques, with double environmental seals and 'enclosed' EMI seal, preventing contact with water. All these changes and improvements helped achieve superior corrosion prevention and control for the EFV."

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