Kaiser Aluminum’s employees ratified a contract.

The United Steelworkers and the Oakland-based company announced ratification of a three-year contract that will significantly reduce wages and benefits for 6,500 workers at a dozen aluminum plants nationwide. The company said the contract includes across-the-board cuts in wages and benefits with a total cost reduction of about $4.50 an hour. Modifications include an average wage reduction of $1.84 an hour, loss of three paid holidays, changes in vacation time and adjustments of health benefits. “The new master contract will save the company about $50 million a year,” a Kaiser official said.