Petroleum coke melt cover for aluminum and magnesium alloys

The instant invention relates to a method of preventing metal loss due to oxidation in molten aluminum and magnesium alloys. Specifically, covering the molten alloy surface with a layer of petroleum coke, which subsequently oxidizes at high temperatures to form a layer of carbon dioxide that insulates the alloy melt from ambient air oxygen, significantly reduces metal loss from the molten alloys due to oxidation. A method for preventing oxidation of molten aluminum alloy and magnesium alloy surfaces, the method comprising providing a molten aluminum alloy or magnesium alloy having a molten aluminum or magnesium alloy surface; covering the molten aluminum or magnesium alloy surface with an initial layer of petroleum coke, the initial layer of petroleum coke having an initial layer thickness of about 0.75 inches; oxidizing a portion of the initial layer of petroleum coke to form a working layer of petroleum coke covering the molten metal surface, the working layer of coke having a working layer thickness of about 0.5 inches, and a layer of carbon dioxide immediately adjacent to and contiguous with the working layer of petroleum coke; and adding additional petroleum coke to the working layer of petroleum coke to maintain the working layer thickness at about 0.5 inches.