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Bonding to Different Metal Substrates
Joining and bonding metals in the design process.
Designing with Metal
For manufacturers, metals are cost-effective, perform well across a wide range of temperatures, show fairly good weather resistance and have excellent strength. End consumers trust metals: they’re solid and sturdy, they’re cool to the touch and cool to the eye. Metals can provide any look you want, from gritty industrial to high tech alloys.
There are seemingly endless ways to shape or process metals: casting, stamping, bending, drawing – even a blacksmith’s forge. You know all this because you know about metal and why you’ve chosen it for your design. We know about metal too, but what we really know is how to bond metal.
Traditional Fastening vs. Adhesive Bonding
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Joining with Mechanical Fasteners vs. Adhesive Bonding
Metal fasteners are almost as old as metalworking, and people are familiar with them. It just “feels right” that bonding metal with a metal fastener is a good choice – but it may not be the best choice. Industrial adhesives provide six key benefits over other industrial assembly methods:
- Eliminate drilling and holes – drilling takes time, and holes make your substrate weaker at that point and become a possible site for corrosion
- Distribute stress evenly across the bond – rather than concentrated stress at one or more fastener points, the substrate is evenly stressed over the area of the bond
- Enable the use of thinner, lightweight materials – because the stress is distributed across the entire bond line the substrate doesn’t need to be as thick to accommodate fastener stress points
- Bond and isolate dissimilar materials – certain mechanical fasteners don’t work well with non-metal substrates, and two different metals can create corrosion problems
- Bond and seal simultaneously – adhesives don’t just bond, they can also keep fluids out or in
- Reduce vibration – resilient adhesives can help dissipate energy rather than transmit it
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Welding / Brazing / Soldering (Thermal Bonding) vs. Adhesive Bonding
Thermal attachments such as welding are familiar and accepted in the marketplace because the consumable materials are inexpensive and thermal bonding is usually faster since there is no cure time. Both thermal and adhesive bonds provide a good bond and seal when done properly. However, adhesives offer several benefits over thermal bonding:
- Enable the use of dissimilar metals – different metals are isolated against galvanic corrosion
- Rework the bond – the bond is easier to disassemble, rework and repair
- Reduce labor costs – adhesives require less workforce training and expertise to get a good bond
- Improve aesthetics – the bonding process does not distort or discolor the substrates
- Enable the use of thinner substrates – because the metal is not distorted a thinner substrate may be just as strong
- Lower energy costs – thermal bonding is very energy-intensive
- Improve worker comfort – most adhesives can be applied at room temperature
Considerations when Bonding Metal
Various factors come into play when considering the best way to bond metal in your process, including rigid vs. flexible, corrosion, thermal exposure and stress concentration.
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Rigid vs. FlexibleA rigid adhesive transmits energy efficiently, such as from a golf club shaft to the head. A flexible adhesive helps dissipate energy, such as vibrations in a passenger rail car, so the structure isn’t adversely affected. Different adhesives are rigid or flexible to a different extent so you can choose the one that’s best for your application.
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CorrosionGalvanic corrosion occurs when a more active metal loses electrons to a less active one, leading to both cosmetic degradation and material failure through rust or pitting; this is a particular problem when a metal fastener easily transmits the electrons. An adhesive can not only bond different metals, but also provide a thin insulation layer to resist this corrosion.
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Thermal ExposuresDifferent materials expand and contract at different rates when exposed to heat or cold, which can seriously affect the structure. A sufficiently resilient adhesive can absorb some of this stress, whether it’s between two different metals or between metal and a non-metal substrate such as glass, wood or plastic.
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Stress Concentration/Drilling HolesDrilling holes doesn’t only take time, it also weakens the substrate and concentrates stress at the edge of the hole. An adhesive, on the other hand, can be applied quickly and distributes stress evenly across the bond.
Adhesive Technologies
These are some of the best adhesives and tapes to use for bonding metals. It is important to choose the strength and durability of the adhesive to suit the requirements of the substrate and application. Learn more about each featured technology using the links below.
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With 3M™ VHB™ Tapes you can maintain consistency from sketch to construction, eliminating distracting visible fasteners. These double-sided acrylic foam tapes quickly and easily form high-strength, long-lasting bonds that build strength over time, and they’re able to bond a variety of different substrates.
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3M™ Scotch-Weld™ structural two-part epoxy adhesives are strong, durable, perform well at high temperatures and resist chemical degradation, making them ideal for industrial applications. These high-strength adhesives can offer excellent impact resistance and enable product design for industries like aerospace, construction and transportation.
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3M™ Scotch-Weld™ structural acrylic adhesives can improve productivity and performance by providing strong, secure bonds with fast cure times and enhanced aesthetics. 3M™ Structural Acrylic adhesives can provide high impact resistance, low odor and up to an 18-month shelf life with no need for refrigeration.
Enter some basic parameters about your assembly such as assembly type, substrates and desired bond strength. Then click View Results to see a customized list of 3M tapes and adhesives you should consider.
Bonding to Different Metals
Metals are easy to bond, but each is unique. These are the major types of metals.
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Stainless SteelStainless steel is an iron alloy with carbon and other metals added for corrosion resistance. Common for household cookware, cutlery, commercial kitchens and food processing, it is also used for surgical instruments, in the automotive and aerospace industries, and for general industrial equipment and building facades. Stainless steel is easy to bond but may need to be cleaned to remove dirt, dust, fingerprints and machine oil.
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SteelSteel is an alloy of iron with a small amount of carbon to increase strength. 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 is actually bonding 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.
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AluminumAluminum is a relatively soft, durable, lightweight, ductile and malleable metal that is easily machined, cast, drawn and extruded. It is nearly always alloyed to improve its mechanical properties. Aluminum resists corrosion because a thin layer of aluminum oxide forms almost immediately when the bare metal is exposed to air. Aluminum often needs to be cleaned or abraded to remove dirt, dust, fingerprints and machine oil.
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Copper-Containing MetalsCopper is a soft, malleable, ductile metal with excellent electrical and thermal conductivity. It is subject to corrosion and should not be in contact with materials that cause or increase corrosion, particularly other metals. Metals that can corrode over long periods of time, such as copper and its alloys brass and bronze, require special consideration when selecting an adhesive. 3M makes specially formulated tapes and adhesives that do not promote corrosion and are copper-compatible.
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