Due to its special properties, aluminium can be used in many different ways. It is light, corrosion-resistant and relatively soft, which is why it is easy to process. It is not without reason that this material enjoys great popularity among do-it-yourselfers and industry.
Like many other metals, aluminium can be bonded with adhesives. When it comes to processing with other materials, glue is a real alternative to other types of joints. Due to the chemical properties, however, there are certain points that must be observed when bonding.
Aluminium bonding - common joining methods
If you want to connect metal parts to one another, you have three main options:
1. Screwing or riveting aluminium
Screwing or riveting aluminium is a simple technique to create a connection. The metal must be drilled for this. It is important that in areas with high corrosion stress, the screwed connection is not a weak point. Measures must then be taken subsequently to prevent crevice or contact corrosion. Sealing the gaps and insulating different joining partners is very important here.
2. Welding or soldering aluminium
Welding or soldering creates a durable and stable connection. To weld aluminium, however, you need a lot of experience and special tools. If the aluminium is heated, this can cause tension in the material and impair its appearance. In addition, different materials cannot be welded together.
3. Bonding aluminium with adhesives
Bonding by gluing with adhesives is easy to learn. In contrast to welding, the material retains its original strength and appearance. Depending on the adhesive and the material, the joint can even be more durable than a weld seam. You only need a two-component adhesive or a structural adhesive.
Important: Adhesive joints should ideally only be subjected to shear stress. This is why an adhesive joint is ideal for overlap or plug-in connections. Peeling or tensile stress should be avoided, as these place an enormous load on the bonded joint.
How is aluminium bonded correctly?
A special feature of aluminium is an self-regenerating oxide layer. This protects the aluminium from corrosion. Unfortunately, this layer is in itself brittle and porous. Without pre-treating, the adhesive bonds with the protective layer, instead of with the aluminium. The protective layer then acts like a separating layer between the adhesive and the aluminium. In the long run, the adhesive can therefore detach itself from the material.
Preparing the aluminium for bonding
The surface must be thoroughly cleaned and degreased. There must be no residue of oil or dirt on it. Here you should use fat-soluble cleaners such as acetone. Afterwards you should no longer touch the material with your bare hands.
Abrade the surface with gritpaper to remove the oxide layer. After mechanical processing, a fresh, chemically active surface forms. This is an ideal substrate for the adhesive. It is best to clean it again of the grinding dust.
After cleaning, do not wait longer than 10 minutes for further processing. Otherwise the oxide layer will form again.
Size of the adhesive area
The surface area of the parts to be bonded should be ten times the thickness of the material. Therefore, aluminium with a thickness of one millimetre should have an overlapping of at least one centimetre. To handle greater strain, the bonding surface must be adapted or increased accordingly. Otherwise optimum adhesion cannot be guaranteed.
Bonding aluminium to aluminium
With aluminium you can roughen the surfaces to be bonded with a coarse sandpaper (120-grit). Due to the rough surface, the adhesive has more area in total to attach to. You still need a two-component adhesive and you can get started. Please see the information provided by the adhesive manufacturer for further information.
In addition to epoxy adhesives, acrylic and polyurethane adhesives can also be used. The use of the corresponding material depends on the treatment time and stress of the material.
Bonding aluminium with other metal or nonmetal
If you glue aluminium with other metals or non-metals, you must use an assembly or structural adhesive. If you apply this to the entire surface, you can save yourself the trouble of sealing it afterwards.