The first thing a beginner should understand about metal bonding is that it isn’t easy. Most metals react with the air, or with each other, or with industrial chemicals. Their smooth surfaces are hard to grip, they conduct shock and vibration and expand with temperature.
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For those reasons, metal fabrication has traditionally depended on laborious processes like riveting, welding and soldering. While many of us have tried to improvise a repair using glue, failures usually outnumber successes.
Today, we have a wider choice. Understanding their strengths and limitations will help you choose the perfect metal bonding adhesive.
Epoxies
Most of us still think of two component epoxies when we need to perform a major domestic repair. However epoxies are far from modern and have many shortcomings.
Their strength depends on them being mixed perfectly in exact proportions, which isn’t realistic for home users mixing a small quantity. In Industry they mix larger quantities – but then they face the headache of applying it all properly before it sets.
Clamping followed by 24 hours curing is also required. In service, epoxies don’t stand up too well to shock, vibration and moisture ingress.
Polyurethanes
Polyurethanes are easier to store and apply than epoxies but need moisture to set – not that easy between sheets of metal. They are poor gap fillers and the parts need careful clamping to prevent the glue simply flowing out of the joint.
Although chemically effective on metals, they lack the strength of a perfectly applied epoxy.
Cyanoacrylates
Superglues are easy to apply and set very quickly. Types are available that have some gap filling potential but generally speaking they need both substrates to fit together perfectly.
Chemically, they are not suitable for every metal combination, can be affected by moisture, and shatter suddenly under impact or vibrations.
Revolutionary new metal bonding adhesive
There is a new class of adhesives that can bond metals to metals or almost any other material. An example is CT1 from C-Tec (https://www.ct1.com/product-applications/metal-to-metal-adhesive/).
These adhesives combine resins similar to those in epoxies with chemicals involved in the production of silicones. The result is a supremely versatile adhesive that can be formulated for a super strong bond, to fill gaps or prepare surfaces. It has the ideal flexibility to withstand shock and temperature fluctuations and is easy to apply.
