The special material attached to the outside of American Virginia class submarines has been peeling off. The special material absorbs sonar signals, making the Virginias harder to detect. This an old technique, dating back to World War II, when the Germans invented the concept and installed it on their subs in 1940. The adhesive attaching the material to the hull did not work so well, and it took the Germans another four years before they developed an adhesive that seemed to hold. But the adhesive problems persisted after the war, and to the present. The adhesive for the sound absorbing (or "anechoic") material on the Virginias was tested extensively, but it still fails under some conditions, after several years of use. The U.S. Navy is now working on finding out what is causing the problem.
Russian subs have long had the same problem, and do not appear to have developed a perfect solution either. When the "anechoic" material comes loose, it actually makes the subs noisier, because of how the water flows over the area where the material has come loose. If the material comes off in strips that stay attached to the sub, that makes even more noise, and the subs becomes even more vulnerable to enemy detection.
The U.S. has similar problems with the anti-radar material used on stealth aircraft. The problem is so severe with these aircraft that they require much more maintenance than non-stealth aircraft, to keep the anti-radar (or radar signal absorbing) material in good repair.
Currently, the U.S. has seven of the new, 7,700 ton, Virginia class SSNs in service, three under construction and plans to eventually build 30. The mainstay of the American submarine force is still the 6,100 ton Los Angeles-class SSN. Sixty-two of these submarines were built, 44 of which remain in front-line service, making it probably the largest class of nuclear submarines that will ever be built. The Seawolf-class of nuclear attack submarines stopped at three from a planned class of twenty-nine. The 8,600 ton Seawolf was designed as a super-submarine, designed to fight the Soviet Navy at its height. Reportedly, it is quieter going 40 kilometers an hour, than the Los Angeles-class submarines are at pier side, partly because of the anechoic material on its hull.