Coating technology enables production of super lightweight magnesium frames

Citation

(2002), "Coating technology enables production of super lightweight magnesium frames", Anti-Corrosion Methods and Materials, Vol. 49 No. 6. https://doi.org/10.1108/acmm.2002.12849faf.001

Coating technology enables production of super lightweight magnesium frames

Coating technology enables production of super lightweight magnesium frames

Keywords: Coatings, Magnesium, Technology

All the conditions are said to be right for magnesium to make the switch from minor metal to commodity status and for the industry to see explosive growth over the next decade. By 2007, Australia is expected to replace China as the largest producer of primary magnesium and global capacity will more than double over the next 5 years. Prices recently reached a record low in real terms, falling below those of aluminium.

Demand for magnesium diecasting has grown by 350 per cent over the past 10 years, fuelled by the growing interest from the automotive sector. Car manufacturers are being forced to reduce the weight of vehicles in order to meet regulatory requirements for reduced emissions. The use of magnesium in the average car is expected to increase from 4 kg per vehicle today to at least 65 kg by 2020, and as much as 150 kg in some models.

The commitment shown by high-volume automotive manufacturers has given companies throughout the magnesium supply chain confidence to invest in further research. This has led to the development of new alloys, greener smelting technology, more efficient casting techniques and more effective surface treatment.

Why the sudden interest in magnesium?

As a raw material, magnesium has always been in abundance. Recent and planned investment in new capacity, particularly in Australia and Canada, has given industries such as the automotive sector now found confidence in the security of supplies of diecasting alloys. This is essential for such a high-volume manufacturer with a lengthy product cycle. The big three car manufacturers have all shown their commitment by entering into long-term supply agreements with magnesium producers.

The car manufacturers also believe that they will see low and stable pricing over the coming years. Large-scale investment in new capacity means that global supplies of magnesium will be in surplus from 2004, causing prices to fall further. Costs throughout the supply chain are being driven down in anticipation of this: modem plants are taking advantage of the latest technology to reduce production costs; new casting alloys and casting techniques have been developed to reduce processing costs and increase productivity rates.

Environmental issues are growing in importance when it comes to the choice of materials.

There was no point in the car industry taking steps to reduce vehicle weight and fuel emissions by incorporating lightweight magnesium components if the smelters were going to continue to use the dangerous greenhouse gas, SF6. New smelting technology is much more acceptable, and this, together with the latest high temperature die casting technology and chrome-free surface treatment technologies have enabled magnesium to win the all-important approval of the green lobby.

New alloys and processing techniques have combined to overcome some of the traditional concerns about the properties of magnesium. There is now a range of alloys with excellent casting qualities in terms of flow properties and melt characteristics. The latest in metal injection moulding technologies are proving very cost-effective. The low density and small draft angles of magnesium make for cheap and rapid machining of high precision parts.

As vast amounts of new capacity come on stream, therefore, supplies of magnesium are more plentiful than ever before and prices are falling as anticipated. Design centres around the world are excited at the prospect of working with such a versatile new material. It can easily be moulded into complex shapes, it is lighter even than aluminium and has none of the problems associated with the highly specialised processing of titanium.

The low density of magnesium means that casting rates are high, and the small draft angle makes near net shapes easy to achieve. Because it has such a low melting temperature and does not react with steel, the lifetime of dies is extended and costs are reduced accordingly. Magnesium requires no special cutting or polishing tools and the welding process is considerably simpler than that associated with titanium.

With so much to offer, why then are so few eyewear manufacturers producing magnesium frames?

The highly corrosive combination of suncream, sweat and cosmetics, particularly in humid climates, has caused eyewear manufacturers to shy away from the use of magnesium as they have never been able to find a surface treatment that could provide adequate protection under such extreme conditions. Keronite Ltd now provides that protection: a layer of only 15 microns of Keronite, applied using the Company’s new plasma electrolytic oxidation process reportedly gives magnesium alloys as much as 1,000 h of corrosion resistance in the extreme environment of a salt spray test.

Not only that, but Keronite is also said to transform the substrate alloy into a hard, dense, ceramic which is extremely resistant to impact and cracking.

The outer layer of Keronite is porous and reportedly provides an excellent adhesive base for subsequent finishing with a topcoat of paint or lacquer. Using Keronite as a pre-treatment in this way can give frames unmatched scratch resistance.

The Keronite process is designed to coat all surfaces of the most complex shapes using robust yet simple equipment together with highly sophisticated electro-chemistry. Unlike many traditional coatings techniques, the electrolyte used in the Keronite process is stated to be non-toxic and at 3-5 microns per minute, deposition rates are very fast.

Keronite Ltd has several years of experience in coating magnesium components for a variety of high-spec automotive and general engineering applications. The company is increasingly being asked to help enable designers in consumer markets to find new applications for magnesium. There has been growing interest in the use of Keronite on electronics products such as mobile telephone and lap top cases. It is no surprise now that manufacturers of fashion accessories such as wrist watches and frames for opthalmic, sports and sunglasses are also turning to Keronite for the enabling technology they need.

Still relatively new to this market, the Company has achieved very rapid success in the field of spectacle frames where designers are constantly seeking new materials as a way of differentiating themselves from their competitors. A growing number of Keronite-coated models are already hitting the market place and it will be these early adopters that benefit most from the novelty value of magnesium.

Keronite Ltd is inspired by the level of interest shown by frame manufacturers world- wide and is working with a number of market leaders to develop the very latest designer frames, particularly those aimed at the fast- growing younger end of the market. It is anticipated that we could soon see in excess of 20 million frames being manufactured in magnesium each year: the buyers of raw materials will be happy; the designers love the endless possibilities now opening up for them; the diecasters, machiners and welders will start to see the payback on their investments; retailers will be able to reduce the amount of capital tied up in stock and hopefully see their margins increase; and the high street? The early signs are that magnesium is just what the market has been waiting for!

Details available from: Keronite Ltd, Tel: +44 1223 893222; E-mail: info@keronite.com