FOCUS ON JOINING match the requirements of a wide range of disparate substrates and applications.
Choosing the adhesive
“ There is no such thing as one adhesive for metals. The properties of the adhesive( such as composition, viscosity or temperature resistance) must be matched to the surface to be bonded. For example, precisely fitting parts where small surfaces are joined together place different demands on the adhesive than, for example, in the case of surface laminations,” continued 3M.
This means choosing an adhesive with low surface tension, because the lower the viscosity of the adhesive, the easier it is to wet the workpiece surface. Most adhesives for metal are therefore two-component adhesives. Acrylic, epoxy and polyurethane adhesives are predominantly used.
It can be challenging to choose the best metal adhesive, given the vast number of options. Each chemistry has its own unique benefits. These include:
■ Structural adhesives, such as structural acrylic adhesives and epoxies, are suitable metal adhesives for forming strong bonds that resist stress, temperature and chemicals.
■ Anaerobic adhesives / sealants are used as threadlockers, pipe thread sealants, retaining compounds or FIP gaskets. Anaerobic adhesives are only used as metal adhesives and sealants. They do not cure on other substrates such as glass and plastic.
■ Cyanoacrylate adhesives develop strength very quickly. These bonds perform well in shear and resist non-polar solvents. Consider structural adhesives if you require an adhesive for metal that provides impact resistance or resistance to polar solvents.
Worker using glue gun with adhesive to fix steel on roof.
■ UV Curable adhesives are suitable for invisible bonds between glass and metal. These are used extensively to bond metal hinges, knobs and fixtures to glass doors.
■ MS Polymer adhesives are suitable for thin sheets of metal, such as truck panel bonding. The low shrinkage provides no read-through( you can’ t see where the adhesive is placed through the panel), providing a good aesthetic finish.
Hot-melt adhesives are also common. These are applied in a molten state approx. 150 ° C- 190 ° C and the parts must be joined before
Epoxy adhesive on metal.
Image: Samaro. Image: Shutterstock. com. the“ melt” solidifies. An example of this is the hot glue gun. Adhesive tapes are suitable for bonding similar and different materials such as metal( e. g. steel, stainless steel and aluminium, also with powder-coated surfaces) with plastic, wood or glass.
Adhesives are increasingly being used in modern automotive production.
“ Adhesive bonding increases the choice of material used and enables more innovative designs; both are important factors for the safety of the car. For example, the windscreen provides structural strength to the car body and helps keep passengers inside the car if an accident should occur. As important as the windscreen quality is, so too is the quality and proper installation of the auto glass adhesive. The use of adhesives in car production helps to improve the safety standards and allows modern design with innovative material. They help the car industry to meet their challenges of developing more environmentally friendly solutions for the future,” commented FEICA.
Material issues
The type of material to be bonded also has an impact. For example, stainless steel may need to be cleaned to remove dirt, dust, fingerprints and machine oil.
Steel surfaces are typically coated before or after bonding to prevent corrosion, either with zinc( galvanized steel) or some type of paint. If coated before, the adhesive bonds to any coating( rather than the steel itself) which affects surface energy and how well the adhesive wets out. Other adhesives and tapes are designed to survive the coating or painting process.
Aluminium resists corrosion because a thin layer of aluminium oxide forms almost immediately when the bare metal is exposed to air. Aluminium often needs to be cleaned or abraded to remove dirt, dust, fingerprints and machine oil. Metals that can corrode over long periods of time, such as copper and its alloys brass and bronze, require special consideration
Image: Shutterstock. com.
ISMR April 2026 | ismr. net | 41