When looking to bond aluminum, it is important to keep in mind that aluminum surfaces often have a weak, invisible oxide layer. Just wiping with a solvent cleaner is not usually sufficient if a high bond strength is sought. Adhesives bond well to the oxide layer – however – the oxide layer isn’t bonded well to the aluminum. It often looks as if the adhesive bond has failed, but on close inspection, it is clear that the oxide layer has just come off the aluminum.
Although solvent wiping in itself isn’t adequate, it is important to solvent wipe before abrading or grit blasting the surface to avoid pushing the oils or impurities into the fresh aluminum. After treatment – wipe the surface again, to remove any debris.
There are a variety of solvents available to consider. Acetone, isopropanol, Permabond Cleaner A are all suitable. Avoid white spirits or meths as they can leave a residue.
Now we are ready to bond the aluminum.
Aluminum (or aluminium – if you prefer) is a soft, lightweight, light-grey metal. Most aluminum is made into an alloy to enhance properties. The type of aluminum will affect the bond strength and adhesive selection. For detailed information on each type, contact Permabond technical support. For reference, we’ve listed the alloy series numbers below.
Anaerobic adhesives -Suitable for close-fitting concentric parts or threaded components. Anaerobic adhesives require active metal to cure; aluminum is passive, so use A905 or ASC10 to speed up the cure. For gasketing / flange sealing, LH197 is a particularly good choice for softer aluminum alloys. Take care to encircle bolt holes properly.
Cyanoacrylate – also known as instant adhesives, super glue, crazy glue, ca glue, etc. All grades will bond aluminum well. For very high strength use a metal bonder such as 170 or the original 910®. For bonding aluminum to dissimilar surfaces with different coefficients of thermal expansion consider toughened 737.
Single component epoxies are ideal for bonding aluminum. Consider ES550 or ES558.
Two component epoxies also form strong bonds to aluminum. Permabond ET515 and MT382 are popular choices for thin panel aluminum bonding as they minimize or eliminate read-through (show-through). Permabond ET5422 is ideal where extremely high shear and peel strength are needed.
Structural acrylics such as TA4246 are very strong aluminum bonders.
UV Curable adhesives are a good choice providing light can reach the entire bond site. Consider UV7141 for applications with shadowed areas.
With so many choices of adhesives for aluminum, the desired cure process, the desired environmental resistance, and the desired temperature resistance are key factors in choosing the best adhesive for each application.
Aluminum Alloy Series Numbers Follow