A Michigan-based firm is working to close a $13 million purchase of Columbus Foundry and its parent company, Intermet Corp., a spokesman said Tuesday. Plymouth, Mich.-based Cerion LLC, owned by Paris, Ky.-based Revstone Industries LLC, was the high bidder for Intermet, which has filed for Chapter 11 bankruptcy twice since 2004. The second time was in August 2008. Cerion’s bid for Fort Worth, Texas-based…