Clark, 65, will be on the board's audit and compensation committees, Corning said. At the company's annual shareholder meeting in April he will be up for election for a one-year term.
Clark served as Merck's CEO from May 2005 through January 2011. He became Merck's chairman in April 2007 and left that role at the beginning of the month.
With the addition of Clark, Corning's board has 14 members.