Comparison of experimental methods to investigate the oxidation behaviour of aluminium melts

Due to high energy savings compared to primary production, recycling of aluminium scrap has become increasingly important in recent years. However, the base metal character prevents a recy-cling economy according to the "zero waste" concept. During melting and holding processes, the liquid aluminium reacts with oxygen in the atmosphere. This leads to the formation of dross and thus to a reduction in the metal yield. To keep these losses as low as possible, casthouses have long been striving to minimise influences that promote oxidation. For this purpose, it is essential to understand the mechanisms behind oxidation, especially in the case of the particularly problematic high Mg alloys, where break-away oxidation can occur. In addition to temperature and holding time, the oxygen content and other gaseous components of the furnace atmosphere have a decisive impact. Bath movement is another factor with major influence regarding oxidation behaviour of aluminium melts. Laboratory investigations on a small scale do usually not allow all these parame-ters to be considered and therefore provide only limited information on the behaviour under indus-trial conditions.
This paper provides a comparison of different experimental setups for the assessment of the oxida-tion behaviour of aluminium melts at the scales < 1 g, 50 g and 30 kg and also addresses the trans-ferability of the results towards industrial processes. Quantification is primarily carried out by means of continuous and discontinuous gravimetric measurements. In addition, a qualitative as-sessment of the oxide layers is performed using scanning electron microscope images.