Utah-based First Security Corp. said Monday it completed its previously announced acquisition Marine National Bank in Irvine. Terms of the buyout announced Oct. 1 weren't disclosed. Marine's former owner, Shinhan Bank of South Korea, paid $13 million for the three-branch institution in 1995. Marine's branches are in Irvine, Newport Beach and Orange. Salt Lake City-based First Security is the second-largest bank holding company in the West.