Gluing instead of welding.
Welding, screwing, and riveting can be replaced in many joints by modern high-performance adhesives, without heat distortion, with even load distribution, and often sealing in a single step. This overview guides you from the joining task to the appropriate adhesive technology, from high-strength structural bonding and anaerobic shaft-hub joining to flexible flange gaskets. SILITECH provides support with selection, data sheets, and brand alternatives, available from stock in Gümligen.
On this page
Why glue? · Technologies · Comparison · Selection guide · By joining task · Selection criteria · Processing · Common errors · FAQ · Further information
Why stick
What gluing offers compared to welding
Modern structural adhesives replace welding in many joints, and they often also replace screws and rivets. Instead of applying force at a single point, an adhesive joint distributes the load over a surface without thermally damaging the base material. This opens up possibilities for joints that would be impossible to weld.
Technically:
- No heat-affected zone, no distortion and no structural changes to the base material.
- Different materials are joined; the adhesive layer insulates and prevents galvanic corrosion.
- Distributing the load over a larger area instead of concentrating it at a notch increases fatigue strength.
- The elastic adhesive layer dampens vibrations and shocks.
- Thin-walled and heat-sensitive components can be joined.
- Joining and sealing in one operation.
Economically:
- No high-temperature process, lower energy and equipment costs.
- No weld rework required.
- Automation and inline dosing are easily implementable.
Particularly useful for mixed joints such as steel with aluminum, for thin sheets, on painted surfaces and anywhere where subsequent disassembly plays no role or is only a planned one.
Technology choice
The adhesive technologies
Six technologies cover virtually every joining task. No single system is universally the best; for every task, there is an optimal candidate.
Epoxy resin (2-component)
Maximum strength
Structural adhesive with the highest shear strength, very good media and temperature resistance. First choice for highly stressed, flat metal bonds. Rather stiff, longer curing time, precise mixing required.
Structural acrylate (MMA, 2K)
Impact resistant, surface tolerant
High impact strength, bridges uneven gaps and adheres even to poorly pre-treated or slightly oily surfaces. Effective with dissimilar materials, aluminum, and composites.
Polyurethan
Elastic, vibration-resistant
Tough-elastic joints with high elongation at break. Dampens vibrations and compensates for differential thermal expansion. For dynamically loaded and crash-relevant structures.
cyanoacrylate
Second fix
It hardens in seconds, without mixing, for small areas and narrow joints. It is not gap-filling and not impact-resistant. Toughener-modified types improve impact resistance, such as rubber-metal.
Anaerobic adhesives
Metal, thread, shaft-hub
Hardening under anaerobic conditions in the metal gap. Securing threads against loosening, joining shafts and hubs, and sealing flanges. Securing and sealing in one step, on metal only.
UV-curing
Glass, optics, positioning
They remain liquid until targeted UV irradiation, then cure in seconds. Ideal for positioning on transparent substrates such as glass and clear plastics, in optics and medical technology.
Profile
Technologies compared
The profile for each technology serves as a guide. Specific key figures are product-dependent and can be found in the data sheet and the linked technical articles.
| Characteristic | Epoxy (2K) | Structural acrylate (MMA) | Polyurethan | cyanoacrylate | Anaerobic |
|---|---|---|---|---|---|
| Shear strength | very high | high | medium | medium | high (in the metal gap) |
| Impact resistance | medium | very high | high | small amount | medium |
| Curing | Minutes to hours | minutes | medium | seconds | minutes |
| Gap filling | very good | very good | good | very low | small amount |
| flexibility | small amount | medium | high | small amount | small amount |
| Substrates | universal | universal, surface-tolerant | many | many | only metal |
| Components | 2K | 2K | 1K or 2K | 1K | 1K |
| Typical strength | highest strength | Impact and difficult surfaces | Elasticity, Crash | Speed, small parts | Thread, shaft-hub, flange |
Rule of thumb: epoxy for maximum strength, structural acrylate for impact and difficult surfaces, polyurethane for elasticity and vibration resistance, cyanoacrylate for rapid fixing of small parts, anaerobic adhesives for threads, shaft-hub and flange. UV-curing systems complete the range for transparent substrates.
Decision
Selection aid
| Requirement | More suitable | Notice |
|---|---|---|
| Highest static strength, across the entire surface | Epoxy (2K) | Surface preparation determines strength |
| Impact, vibration, mixed connection | Structural acrylic or polyurethane | surface-tolerant, elastic |
| Quick fixing, small parts | cyanoacrylate | tight joint, not for impact and vibration |
| Secure threads | anaerobic screw locking | Strength class according to disassembly requirements |
| Shaft-hub, bearing seat | anaerobic adhesive | Replaces press fit, larger tolerances possible |
| Flexible flange sealing | RTV silicone (FIPG) or anaerobic flange sealant | Consider gap, medium, and stiffness |
| Transparent substrates, positioning | UV-curing | at least one substrate is UV-permeable |
| Later disassembly required | medium-strength anaerobic systems, soluble adhesives | Do not use high-strength epoxides |
Key factors include material pairing, gap dimensions, type of load, temperature, media contact, and disassembly requirements. Specific parameters can be found in the respective technical data sheet.
After joining task
Typical joining tasks
What is required in practice, and which technology contributes to meeting that need.
Structural bonding of metal
flat, high strength
Load-bearing metal connections instead of welds, with uniform load distribution and no heat distortion. Typically epoxy or structural acrylate. Adhesives & sealants.
Shaft-hub & bearing seat
anaerobic, replaces press fit
Gear, pulley, or bearing on the shaft and in the housing. Anaerobic adhesives replace press fits and shrink fits, allowing for greater tolerances. Shaft-hub in detail.
Screw locking device
vibration-proof, sealing
Secures threads against loosening due to vibration and seals simultaneously. Select the strength class according to disassembly requirements, from low to high. Select threadlocker.
Flange gasket (FIPG)
flexible, formed in place
Gasket applied directly to the flange instead of a pre-fabricated flat gasket. RTV silicone or anaerobic flange sealant, depending on the gap, medium, and stiffness. Flange gasket details.
Quick fixation & small parts
Seconds, without mixing
Fast fixing of small parts, rubber-to-metal and O-rings. Cyanoacrylate, toughened types for impact or peel stress. Cyanoacrylates available in our shop.
Multimaterial & Composite
Mixed compounds
Bonding metal to plastic, GRP, CFRP or glass, even with differing expansion rates. Structural acrylic, polyurethane or UV. World Bonding & Sealing.
specification
What you should clarify before making your selection
- Material pairing: which materials, active metals such as steel and copper or passive metals such as stainless steel and aluminum.
- Gap size: narrow joint or tolerance compensation severely limits the technology.
- Load: static, dynamic, impact, peeling, and the required strength with safety factor.
- Temperature: Continuous and peak temperature as well as temperature changes.
- Media: Oil, fuel, cleaner, moisture or chemicals at the joint.
- Curing and cycle time: Fixation and final strength appropriate to the process.
- Disassembly: the connection should remain detachable.
- Approvals: for example NSF and WRAS (drinking water), DVGW (gas and water) or industry-specific certifications.
- Processing: Dosage, quantity, manual or automated.
Using this information, we will jointly narrow down suitable products and review the data sheets.
processing
Process cleanly
The strength of an adhesive bond is largely determined at the surface. Clean, well-defined preparation is more important than the last decimal place in the data sheet.
- Cleaning: degrease with isopropanol or suitable cleaner, wipe lint-free and in one direction.
- Activation: Roughening or blasting the surface significantly increases the effective area and improves adhesion.
- Primer and activator: for difficult substrates such as stainless steel, aluminum, or paint. Anaerobic adhesives only cure reliably on passive metals with an activator.
- Dosing and mixing: for 2K systems, the mixing ratio must be adhered to precisely; static mixers or dosing technology ensure reproducible quality.
- Joining and curing: join within the open time, align position before fixing, wait for final strength according to the data sheet.
- Safety: Observe gloves, ventilation and the safety data sheet.
From practice
Common mistakes
- Surface preparation is underestimated: the most common cause of premature failure.
- Incorrect strength class for screw locking: high strength where disassembly will later be necessary.
- Cyanoacrylate under vibration or impact: brittle joint, the connection breaks.
- Anaerobic curing on stainless steel or aluminium without activator: significantly prolonged curing time and reduced strength.
- Too rigid a system on thin sheet metal or mixed joint: stress cracks due to differential expansion.
- Flange gasket subjected to stress too early: leaks before hardening.
FAQ
Frequently Asked Questions
Does an adhesive bond hold as well as a weld?
When properly executed, adhesive bonds achieve a very high level of static strength, and under dynamic loads the elastic adhesive layer demonstrates its strength by dissipating stress peaks. The bonding surface, adhesive selection, and surface preparation are crucial.
Can a glued joint be undone?
It depends on the system. Medium-strength anaerobic adhesives can be dissolved with tools, high-strength ones with heat. Cyanoacrylate can be broken down with a special solvent. High-strength epoxies are practically insoluble. Factor disassembly into your material selection.
Does gluing work on galvanized or painted metal?
Yes, with proper preparation. Clean and lightly roughen galvanized surfaces, sand paintwork, or test paint adhesion to the base material. On difficult surfaces, a primer significantly increases durability.
What do active and passive metals mean in anaerobic adhesives?
Active metals such as steel, copper, and brass directly catalyze the hardening process. Passive metals such as stainless steel and aluminum slow it down; in these cases, an activator ensures reliable and rapid hardening.
Can I use Permabond instead of Loctite?
In most cases, yes. For many Loctite types, there is a comparable Permabond product, often more cost-effective with the same performance. We advise on switching and provide the appropriate equivalent.
Gluing the shaft-hub instead of pressing it in – what are the advantages?
Anaerobic adhesives allow for larger manufacturing tolerances, distribute the load evenly across the bonding surface, and prevent thermal stresses from shrinkage. The bond remains heat-disassemblable.
Further information
Matching products, worlds, articles & industries
Product groups: Adhesives & sealants · Epoxy adhesives · Structural adhesives (MMA) · Cyanoacrylates · Anaerobic adhesives · UV adhesives
Themed areas: Adhesives & Sealants · Silicones
Knowledge articles: Bonding metal without welding · Industrial adhesives compared · Permabond and Loctite compared · Shaft-hub connection · Threadlockers · Flange gasket (FIPG)
Industries: Mechanical Engineering · Electronics & Printed Circuit Boards · E-Mobility & Batteries · Energy & High Voltage · Aerospace · Defense & Security
Terms: in the glossary (shear strength, gap bridging, anaerobic, cyanoacrylate, FIPG, structural adhesive).
Technical basis: The information provided is for general guidance only and does not constitute a product guarantee. The manufacturer's data sheets (TDS) and relevant standards are binding. Specific characteristics (shear strength, temperature range, gap bridging, pot life and setting time) are product-dependent.
contact
Unsure which joining technique is right for your joint?
Describe the materials, gap dimensions, load, and environment. We will check suitable adhesives, technical data sheets, and alternatives, including availability from our Gümligen warehouse.