Aluminium needs to be welded using a hot and fast technique, where the welding tool is run at a higher amperage and held in on a spot for less time as compared to welding with steel. Preheating and cleaning aluminum surfaces before welding is also required for the best results.
Aluminum welding procedures differ from steel welding largely due to the differences in thermal conductivity between the two materials. Aluminum has a higher thermal conductivity than steel, so leaving a welding tool in place for long periods has the potential to damage the metal. Pushing the welder away from the pool of molten weld, rather than pulling it along the weld, helps strengthen the weld by preventing contamination of the welding material.
Proper preparation of aluminum surfaces for welding is essential, as aluminum forms oxides on its surface that have a higher melting temperature than the interior of the metal. The presence of this oxide prevents the welding material from penetrating effectively into the weld, so it is recommended that the area welded is thoroughly cleaned of oxide with a stainless steel wire brush or solvents before beginning to weld. Preheating the surface to 230 degrees Fahrenheit is also useful to prevent cracking of the weld.