Treatment of ingots or spacer blocks in stacked aluminum ingots

A method of treating a surface of a stacked aluminum alloy ingot during a heating process comprising the steps of:

• positioning a spacer member adjacent an aluminum alloy ingot to form a stack, wherein the spacer member comprises a support surface contacting a contact surface of the aluminum alloy ingot, and at least one of the support surface and the contact surface comprises a fluorine containing material;
• and
• heating the stack to at least a temperature at which the fluorine containing material decomposes or vaporizes and an alloying metal in the aluminum alloy ingot migrates to the contact surface such that a layer of a fluorinated oxide of the metal forms on the contact surface.