Abstract: The invention provides a process for preventing the oxidation of liquid zinc, while at a temperature exceeding 500.degree. C, in a furnace heated by natural gas and utilizing at least one furnace burner, by injecting into the furnace atmosphere comprising air containing free oxygen (preferably an amount of free oxygen of less than 1.5% by volume), a quantity of sulphur dioxide in an amount between about 0.01% and 0.04%, by volume (preferably about 0.02%, by volume) with respect to the volume of the furnace atmosphere. The sulphur dioxide may be provided by low grade gases from a lead foundry or may be produced by the combustion of a sulphur-containing material.