Archive: August 2010

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.