Tack welding is the process of creating a small weld spot to join two pieces of metal either temporarily during the construction process to hold them in place until another weld can be made, or the process of spot welding two pieces together in a number of places so that a finished weld is not required. Tack welding aluminum can be a difficult process because aluminum has a fairly low melting temperature and does not respond well to most welding processes. There are a few simple steps to tack welding aluminum that ensure that your project will go smoothly and that you won't ruin your work piece by burning through or melting it.
Select the proper equipment. There are two types of welding equipment that can be used to weld aluminum. One is a MIG welding setup with the proper aluminum wire operated out of a spool gun at the end of the welder. This method is excellent for welding aluminum quickly and easily, especially if you are already familiar with the process of MIG welding. A second, more involved method is the TIG welding method, where a different type of welder is used, along with aluminum rods that are melted to tack the work piece together.
Melt the metal rod or wire against the two pieces of metal you are attempting to join until they have pooled together. You can either do this using a heat sink compound such as that sold by welding supply companies, or using a copper "spoon" tool to pull heat away from the rest of your work piece while you make the tack weld. he goal is not to spend too long welding in one place or you will burn through the aluminum and create a hole. Using a heat sink will also help to prevent discoloration of the metal that you are welding.
Stop applying heat to the welding material and pull the end of your tip away from the work piece. Once the weld has cooled, you can clean and process the finished weld. This involves using a wire brush to remove any arc spatter or excess metal from the area around the finished weld, as well as any smoke or leftover contamination from the melted welding rod that may still be around the area that was welded. After cleaning, you can inspect the weld to make sure it looks solid.