Aluminium

In the present-day search for greater economy in the running of motor vehicles,whether private,public or commercial,the tendency is for manufacturers to produce bodies which,whilst still maintaining their size and strength,are lighter in weight. Aluminium is approximately one-third of the weight of steel, and aluminium alloys can be produced which have an ultimate tensile strength of 340–620MN/m2. In the early 1920s the pioneers of aluminium construction were developing its use for both private andcommercial bodies; indeed,the 1922 40hp
Lanchester limousine body had an aluminium alloy construction for the bulkhead and bottom frame,and aluminium was used for all the body panels. Before the Second World War aluminium was used mainly for body panels,but since the war aluminium alloys have been and are now being used for bodystructures. Although aluminium is more expensive than steel,it is easy to work and manipulate and cleaner to handle. It also has the advantage of not rusting,and,provided that the right treatment is adopted for welding,corrosion is almost non-existent. In recent years the use of aluminium and aluminium alloys for motor bodies,especially in the commercial field,has developed enormously.
In the modern motor body the saving of weight is its most important advantage,and although on average the panel thickness used is approximately double that of steel,a considerable weight saving can be achieved. One square metre of 1.6mm thick aluminium weights 4.35kg while one square metre of 1.00mm thick steel weighs 7.35kg; the use of aluminium results in a saving in weight of just under 40  percent.
The non-rusting qualities of the aluminium group are well known and are another reason for their use in bodywork. An extremely thin film of oxide forms on all surfaces exposed to the atmosphere,and even if this film is broken by a scratch or chip it will reform,providing complete protection for the metal. The oxide film,which is only 0.0002cm thick,is transparent,but certain impurities in the atmosphere will turn it to various shades of grey.