Cars, like people, tend to get heavier as they get older. It is an issue that preoccupies Werner Stelzer, a senior executive adviser with Rio Tinto Alcan, one of the world's largest aluminium companies.
For the past 20 years as an executive with various vehicle divisions of large aluminium companies, he has been trying to get more aluminium into cars.
But despite his efforts, European cars have gained weight. The current VW Golf series V, for example, is about 60 per cent heavier than the first version, which was introduced in the mid-1970s, although the car is slightly bigger.
But now that the vehicle industry is facing pressure to make lighter cars - mainly for environmental reasons - he thinks the aluminium industry can make some headway.
'The car industry has the potential to be a big driver for the aluminium sector,' Stelzer said on the sidelines of the Metal Bulletin Asian Aluminium and Copper Conference held in Hong Kong recently.
It could do with a boost. Aluminium production and prices plunged from the highs of last year, along with other metals. After peaking at US$3,070 per tonne in July last year, aluminium prices dived to US$1,329 in February. Metal prices have shown some strength in recent months on positive signs in the global economy and aluminium prices have risen to about US$1,930. Production is expected to fall slightly this year, the first decline in about 15 years.
Aluminium is one of the leading substitutes for steel. When mixed with small amounts of other metals to form alloys, it has the strength of steel but only one-third of the weight.
According to the London-based International Aluminium Association, the use of lightweight aluminium components in a vehicle can save six to 12 times the energy taken to produce the primary aluminium used in its construction. Up to 8 per cent fuel savings can be realised for every 10 per cent reduction in weight. One kilogram of aluminium, used to replace heavier materials in a car or light truck, has the potential to eliminate 20kg of carbon dioxide over the lifetime of the vehicle.
Almost 60 per cent of the weight increase in cars occurs in the frame and body, 20 per cent in the suspension and 11 per cent in the electrics. The main cause for the increase has been safety, which accounts for 30 per cent of the rise, legislation 25 per cent, comfort 22 per cent, interior equipment 18 per cent and quality.
Aluminium has been used in cars since the 1920s with European car builders such as Ferrari, Bugatti and Aston using it in limited production runs. During the second world war and its aftermath, aluminium was used in vehicles such as the Land Rover as steel was in short supply.
The first time aluminium was used in mass production, Stelzer recalls, was about 20 years ago for the hard top of the Mercedes SL sports car. 'The specifications stipulated it was to be light enough for two women to lift it.'
Since then, aluminium has increasingly been used in vehicles, culminating with the Audi A2 in which almost the whole car was made out of aluminium.
Aluminium is still mainly used in luxury cars, but its content in mass-produced cars is increasing. A study in 2007 by Knibb, Gormezano & Partners in co-operation with the European Aluminium Association showed that the amount of aluminium in European cars had risen from 50kg in 1990 to 132kg in 2005 and would grow a further 25kg by 2010.
Compared with steel, aluminium offers better fuel efficiency as a result of its lower weight and superior road handling owing to better torsion stiffness. Aluminium is also superior to steel in its ability to absorb energy in a collision and transfer it away from the vehicle occupants.
Another advantage is recycling. Although aluminium production requires a lot of electricity, it is 100 per cent recyclable and, because of its relatively low melting point, requires only 10 per cent of the original electricity.
But there are also obstacles to its use. Aluminium is five times more expensive than steel by weight. Its non-ferrous quality requires different manufacturing processes from steel, which can easily be moved around by magnets.
Another obstacle has been the response of the steel industry, which, rather than stand back and watch the aluminium industry eat into its share of the automotive market, has responded by introducing new lighter grades of steel.
As a result, aluminium has mostly been used in high-end cars such as Rolls-Royce, Ferrari, Honda, Audi, Mercedes and BMW.
For the aluminium industry to experience a significant benefit from the vehicle industry, it needs to be used to build the body and frame of a mass-produced car.
'If the VW Golf is to start manufacturing its bodies and frames from aluminium, the impact on the aluminium industry will be enormous,' Stelzer says.
He believes government pressure for better fuel efficiency and more stringent recycling will lead to aluminium eventually becoming the primary material of car frames and bodies.
For the moment though, mass-market cars are likely to be made of steel with the doors, bonnet and boot made of aluminium.
But as cars such as Audi and the VW Passat become more aluminium-intensive, this will have a big knock-on effect for the aluminium industry as these cars are also made in China where car ownership is soaring. 'The potential for the aluminium industry will be enormous,' Stelzer says.