The U.S. Navy has discovered "aggressive" corrosion in Austal Ltd.'s first new combat ship designed for operating close to shore. The corrosion is in the propulsion areas of the USS Independence, the Littoral Combat Ship built by the Mobile, Alabama-based subsidiary of Australia's Austal and General Dynamics Corp. "This could be a very serious setback," said Norman Polmar, an independent naval analyst and author in Alexandria, Virginia.