Traditionally, connecting aluminum parts together has meant riveting, soldering or welding for a long time now. But increasingly, adhesive options are expanding in common use. Even in automotive and aircraft construction, lightweight components made of aluminum are increasingly being glued these days. It's not only faster and easier, but it also often ensures significantly higher strength. However, before gluing aluminum, there are some rules and special considerations to be made and rules to adhere to.
The bonding of aluminum with aluminum is the domain of two-component adhesives. PUR glue with primer, epoxy resin adhesive, methacrylate adhesives and MS polymers are used here. The process used here is referred to as "contact bonding" - in which both parts have glue applied at the adhesive points, and are firmly compressed after a certain aerating time. This aerating time must be adhered to precisely as it is necessary for the solvent contained in the adhesive to evaporate. For this reason, it is important to proceed exactly as directed by the adhesive manufacturer. In addition, it is crucial to observe the pot life, i.e. the time window within which the adhesive must be processed. Furthermore, the adhesive bond may only be loaded after the specified hardness time has elapsed. The moral of this story is, these products have specific instructions for good reason.
The careful preparation of the surfaces is also extremely important when bonding aluminum surfaces with one another. They must be clean and, above all, absolutely free of fat. Grease and dirt act as release agents and prevent flawless adhesion of the glue. In addition, there is the natural oxidation of aluminum, which forms automatically as soon as the material comes into contact with air. This always-present, wafer-thin oxidation layer impairs the adhesion of the glue and must therefore be thoroughly removed. Overall, the surface preparation and the adhesive process must be completed within about 10 minutes, otherwise there is a risk that an oxidation layer will form again. The procedure should be done in the following two steps:
1) First, both surfaces should be roughened with a sanding paper with 80s or 100s grit. The resulting residue particles must then be removed.
2) Then, a grease or silicone cleaner is then used to free the surface from any grease deposits.
And Voila, you've got a nice, clean, glue ready set of aluminum components. Just don't forget to follow the instructions on your adhesive. Happy gluing!
*For experts, the exact procedure for gluing aluminum is regulated in VDI Directive 2229. It also states that adhesive joints on aluminum components may only be used on thrust and parallel to the joining surface. A rule that can be largely ignored in the home area.