Introduction

AM-cover™ is a low-cost, safe and environmentally friendly cover gas system, which protects molten magnesium from burning and oxidation. It was developed to replace the common SF6 cover gas mixtures, which are being banned in most nations due to their severe environmental effect.

AZoM - Metals, Ceramics, Polymer and Composites - AM-cover - An Environmentally Friendly Cover Gas System For Protection of Molten Magnesium from Advanced Magnesium Technologies

SF6, or sulphur hexafluoride, has the highest Global Warming Potential of all greenhouse gases. Emitting merely one tonne of SF6, which stays in the atmosphere for over 3000 years, is as harmful as releasing 22,000 tonnes of carbon dioxide into the atmosphere. AM-cover is not only significantly more environmentally-friendly than SF6, it is much cheaper and has several operational advantages.
Carbon Trading Benefits from AM-cover™

AMT has formed a Joint Venture with Hyder Consulting to provide AM-cover technology together with specialist project structuring services. The JV will enable the global magnesium industry to utilise savings in greenhouse gas emissions to generate Certified Emission Reduction units under the Kyoto Protocol and trade these on the global carbon market. This will enable magnesium industries in many countries to generate additional revenue streams while replacing SF6 with AM-cover.
What is AM-cover™

AM-cover is an environmentally friendly cover gas system for protection of molten magnesium from ignition and excessive oxidation.

Molten magnesium is a highly reactive metal that unlike many other metals (e.g. aluminium), is not well protected from further oxidation by its own natural oxide film. Thus, molten magnesium burns in air unless it can be protected by some means. Cover gas systems act to change the characteristics of the oxide film so that the film adheres well to the underlying molten magnesium, self-repairs when disturbed or broken, and provides effective protection from further oxidation.
Commercial Driver

Loss of magnesium metal due to oxidation decreases the economic performance of die casting plants and increases environmental problems arising from difficult-to-recycle dross and sludge. The choice of an effective cover gas system, together with efficient furnace closures and melt handling systems, enables molten magnesium to be handled without excessive oxidation or burning and provides an opportunity for die casters to reduce costs.
Environmental Driver

Sulphur hexafluoride (SF6) is the most widely used means of protecting molten magnesium and its alloys from burning. At the time of its introduction in the 1970s, the use of SF6 for this purpose was a significant breakthrough for the magnesium production and die casting industry. However, SF6 has an extremely high Global Warming Potential (GWP), with a CO2-equivalent 22 200 times greater than carbon dioxide. It is listed in the Kyoto Protocol as a gas to be reduced in industrial usage. The EU and a large number of nations, including USA, are undertaking measures to ban or strictly limit its use for the protection of magnesium. An EU directive will ban the use of SF6 for protection of magnesium by all users, whose consumption of SF6 exceeds 500 kg pa, from January 2008. The global magnesium industry is looking for an environmentally friendly solution.
Commercial Opportunity

There is a significant market opportunity for a cover gas system that performs the same function as SF6, has a potential for cost-reduction, and does not have the environmental disadvantages of SF6.
Development History

AM-cover was developed by the former Australian Magnesium Corporation and CAST in a 4 year program of research and development. The technology has now been taken over by AMT and has been extensively tested in a range of industrial environments. AM-cover is being promoted in the market by AMT as an effective replacement for SF6 cover gas mixtures. It is a low cost, safe, and environmentally friendly cover gas system that has been shown in a joint program with the US Environmental Protection Agency (USEPA) to reduce greenhouse gas emissions by more than 99% compared to normal practice with SF6 gas mixtures. Several die casters in North America and Europe have either converted their entire operation to AM-cover or are in the process of converting. The USEPA recently recognised AMT’s contributions to US industry by awarding it a Certificate of Recognition for the introduction of this new environmentally friendly technology.
Widely used as a Refrigerant

The active chemical constituent of AM-cover is HFC-134a which is widely used as a refrigerant gas and is commonly present in automobile air conditioning systems. AM-cover uses HFC-134a in a dilute mixture with a carrier gas such as N2 nitrogen or CO2 carbon dioxide. HFC-134a has a GWP of 1320 but, in the high temperature furnace environment above molten magnesium, 80-90% of the HFC-134a that is used in AM-cover decomposes so that total greenhouse emissions are kept to a minimum. Use of AM-cover for magnesium melt protection typically results in a 95-99% reduction of greenhouse gas emissions compared to SF6 cover gas mixtures and reduces costs by minimising the generation of dross and sludge. The cost of the gas itself is also cheaper than SF6.
Health and Safety

Much of the research on AM-cover has been concerned with thermal decomposition products and associated occupational health and safety issues. Extensive laboratory experiments and industry-scale trials have characterised the decomposition process and enabled the development of safe operating conditions. This work has been independently renewed and approved by an Associate Professor of Medicine and Respiratory Physician at a leading Brisbane hospital.
Patents

Worldwide patents have been applied for to protect the AM-cover technology. Patents have already been granted in a large number of jurisdictions, including Europe and USA. AMT has exclusive worldwide rights to commercialise the user of AM-cover.
Current Status

Marketing of the technology to date has mainly taken place in Europe. Die casters in Europe are particularly interested in the technology because of the forthcoming EU ban on usage of SF6 that is planned to come in effect from January 2008. The main competing technology involves the use of sulphur dioxide which, while cheaper, is harmful to health and contributes to pollution from acid rain. To date seven die casters have signed licence agreements for use of AM-cover and a number of these are already in the process of implementing plant-wide conversions. The technology is licensed under long term agreements at a benchmark price of EUR 10 per tonne of castings produced per annum. There are currently approximately 150,000 tonnes of magnesium castings produced annually. It is expected that over the next few years AM-cover will become the technology-of-choice for the whole magnesium industry, including producers, recyclers and die casters.