Our theoretical model for the effective action cycle of the passivation reaction with SO2-based protective gas mixtures was tested at laboratory scale as well as in industry applications at friendly customer’s plants.
Technically, the measurement of gas components is based on infrared spectroscopy (FTIR), while oxygen is measured paramagnetically.
The composition of the protective gas which is supplied and discharged was correlated with the condition of the passive layer of the magnesium melt. To check its condition, samples were taken from the surface of the bath and analyzed using scanning electron microscopy in combination with energy dispersive X-ray spectroscopy (SEM-EDX).
Our research shows a significant passivation of the liquid magnesium during ingot casting of pure magnesium under open atmosphere and high temperature operations (780 °C) for low-pressure and special alloying applications.
Current long-term operations are aiming for the decrease of dross and sludge during melting processes in large scale Mg-furnaces. Besides an increase in the worker’s safety and comfort the main goal is to make the Mg-casting operations more compatible. At the same time, excessive use of protective gas is prevented, which means that the worker’s exposition to the gas is below the national regulations (MAC). Furthermore, the economics as well as the environment benefits from an efficient use of protective gas.
By the sustainable substitution of partly or perfluorinated gases like HFC-134a and SF6 with the newly developed SO2 based gas mixture for global magnesium applications, the total reduction potential on CO2 equivalents is aimed to be 273,000 metric tons of CO2 per year.
