Aluminium Welding is normally when there is some significant damage to the wheel and therefore we would tend to perform a weld repair. This is because the objective is to create a strong repair without softening the alloy itself. Situations where a wheel weld is appropriate include: - cracks - splits - chunks of rim missing - bent out of shape. 
As with all of our alloy wheel repair services we will only weld a wheel where we are confident that the repaired wheel will be safe for everyday use. If we have any concerns about potential risks then we will tell once the wheel has been fully inspected to see if the welding process is appropriate. The damaged area will be cut and shaped to be welded and then will be welded inside and out using state of the art welding equipment, which minimises the amount of heat transferred into the alloy but with the intention of maximizing the strength of the weld without softening the alloy. 
Important notes as explained, the process of welding a alloy wheel involves heating the damaged area to apply the weld. On the inside of the wheel this may not be visible but on the outside then highly likely that the paint finish will be effected. In these cases the recomendation is to have the wheel fully refurbished.