I’m often asked the question, ‘Which is the best method for joining aluminium?’
The answer is ‘It depends’. It’s not a question of which one is best but rather understanding the pros and cons of each process and relating this to the intended application.
On this occasion we will consider welding. Welding is one of three principal methods by which aluminium parts can be successfully joined together. Bonding (structural adhesives) and using various mechanical means (cleating, folding, nuts/bots, screws, rivets, etc.) are the alternatives.
Welding is often rightly thought of as one of the strongest and most permanent joining methods. This heat intensive process involves fusing separate aluminium items together and then using a filler to form a joint. There are different techniques for welding aluminium (MIG & TIG). The material thickness of the parts to be welded will often determine the most suitable mode.
When considering welding, however, as a preferred joining method ‘casuality’ (cause and effect) should be borne in mind. The event of welding can change the localised form and appearance of the aluminium. For many applications these considerations are of little or no consequence, but where aesthetic considerations apply, care should be exercised. It is always good to know in advance what visual and other effects might manifest from a process.
One of aluminium’s primary advantages is it’s resistance to atmospheric corrosion.
This corrosion resistance is due to the oxide coating that naturally forms on aluminium’s surface.
The aluminium oxide coating has a much higher melting point (2037 C) than the aluminium base metal (648 C)and therefore needs to be removed before welding takes place. Oxide removal is usually achieved by means of using a wire brush or solvents and etching solutions immediately prior to the welding process.
For those in the know, great; but for those that don’t, the question surely arises – What is the connection between Charles Goodman and Aluminium Houses?
Charles Goodman was a Washington DC based architect who specialised in designing homes in the modernist style. Inspired by, amongest others, the Bauhaus work of Mies van de Rohe, Goodman was appointed in 1957 by Alcoa (The Aluminum Company of America) to design the ‘Care Free House’. This collaboration was set up to demonstrate aluminiums‘ suitability and versatility as both a decorative and structural material within residential environments. It was also intended to display how successfully aluminium integrates with traditional materials such as brick, glass, stone and wood.
However ‘green fingered’ or not, most of us would probably acknowledge a basic understanding of the way living plants progress through a life cycle, changing their forms as part of the process. Remarkably, for an inanimate material, aluminium also has the sustainable and environmentally friendly capability of changes in form, passing through potentially numerous life cycles by being recycled from one product into another. No wonder aluminium is called the greenest of metals!
For another ‘natural’ analogy you can also consider comparing aluminium with secondary clay. Both materials, originating from the earth’s crust, are in abundant supply; both are solids and yet lend themselves to changes in form through cold working and/or various forms of heat treatment. Interestingly there are clay building products that can be recycled by composting, while aluminium is recycled through re-melting and manufacturing into new shapes and products.
The worldwide annual recycling of aluminium is very much expanding with a three fold increase from 5 million tonnes in the early 1980’s to something in the region of 15 million or more tonnes in the mid naughties. It is currently estimated the construction industry is recovering over 90% of the aluminium used in redundant buildings (96% of the aluminium from the old Wembley Stadium was recycled).