Oxidation: in air aluminium
immediately forms an oxide layer on its surface, which will increase in thickness with time. This
oxide layer must be controlled during the welding process, by chemically and mechanically cleaning
the metal, using an aggressive flux or ensure that the arc has reverse polarity (electrode
positive). Correct gas shielding (argon) will prevent oxides reforming in the weld.
Thermal: as aluminium is a very good thermal conductor it will rapidly
disperse heat. Care must be taken to avoid distortion or possibly cracking.
Colour: unlike steel, there is no change in colour as it is being
treated. Look out for a ‘wet’ appearance. For gas brazing, melting of flux powder is a temperature
Preparation: smooth all edges of workpiece to minimise trapped dirt. Use
a commercial degreaser and stainless steel brush to remove dirt, oil and paint. Dry the surface
thoroughly. If TIG welding, wipe the filler rod clean of any surface oil.
Application: support the joint to be welded, preferably with a jig, but spot tacking
can be used. Keeps the arc travelling at the right speed to build up a bead of the right
proportions. Do not stop/start on one weld as this can lead to oxidation/porosity. Carry out the
weld quickly to avoid distortion.
Consumables for MIG and TIG welding:
4043A (no.15): contains 5% Silicon, for castings and heat treatable alloys 6063, 6061 and 6083.
Weld will discolour if anodised. Good all purpose rod.
5356 (no.27): contains 5% Magnesium, for similar 5xxx alloys and heat treatable alloys 6063, 6061
and 6083. Has good corrosion resistance.
For pure aluminium, military, aerospace or significant load-bearing applications please contact us
and we will advise on the correct rod for any given application.