A significant amount of aluminum is processed by melting secondary aluminum that contains small amounts of magnesium. A major drawback of aluminum production in secondary melt furnaces is the formation of dross or aluminum oxide by the oxidation of the molten metal. Since aluminum scrap forms a major source of the metal in secondary aluminum processing, the presence of alloying elements plays a key role in the oxidation process. Here, we consider the early stage during the oxidation of Al-Mg alloys during which the primary oxidation is that of magnesium to magnesium oxide occurs. We have simulated the processes in an aluminum melting furnace and considered the metal oxidation to be limited by one–dimensional diffusion. Our results predict the temporal variation of the oxygen distribution and the rate of metal evaporation and formation of the metal oxide. The effects of melt composition, gas temperature and oxygen concentration in the gas are discussed.