METAL TO METAL BONDING WITH PLEXUS® ADHESIVES
INTRODUCTION TO METAL TO METAL BONDING WITH PLEXUS® ADHESIVESJoining metal to metal is a common phenomenon. Design engineers have been joining metal to metal for years. There are several factors engineers consider when joining metals:
- How much force will the joint see?
- How long is the joint expected to last?
- Will the joint be permanent?
- How long will it take to assemble?
- How much will it cost?
- What type of labor will it require?
- Continuous Connection -> Adhesives uniformly distribute stress, improving not only the joint strength, but overall durability. Rivets concentrate the stress, weakening the joint and reducing the overall durability.
- Fast Assembly -> Dispensing an adhesive is fast; often they are significantly faster than traditional joining methods. Rivets typically require pre-drilling and placement of the rivets. Welding, especially aluminum welding, requires thorough surface cleaning before starting work. With Plexus adhesives, there is little to no surface prep needed.
- Dissimilar Material Joining -> Plexus adhesives can join metal to a wide variety of materials. Unlike welding, Plexus adhesives can join stainless steel to aluminum, or G90 to cold rolled steel without galvanic corrosion. Plexus adhesives are significantly stronger than rivets when joining metal to thermosets, thermoplastics, and fiber reinforced plastics.
- Stiffer Structures -> continuous bond area and great surface area of connection means a stiffer structure. Alternatively, the metal can be downgauged and stiffness maintained.
- Improved Surface Appearance -> With Plexus adhesives there are no visual fasteners or surface distortions. Just a clean, smooth surface.
- Corrosion Protection -> Plexus adhesives join and form a water tight seal in one step. There are no leak paths. Additionally, the adhesive provides a barrier to electron transfer of two different materials, preventing galvanic corrosion.
- Reduced weight -> Metal to metal joints formed with Plexus adhesive are often lighter than joints formed with rivets or welding.
STRENGTH OF PLEXUS ADHESIVES VS WELDINGPlexus adhesives have successfully replaced welding in a variety of structural applications. Continuous weld lines often lead to significant heat distortion and heat effected zones on the sheet metal. These distortions can weaken the overall strength and durability of the joint. As a result, the strength of a weld can vary significantly compared to bonding metal to metal with an adhesive. Consider the large standard deviation in lap shear strength of a welded aluminum joint compared to that of the same joint made with Plexus adhesive.
STRENGTH OF PLEXUS ADHESIVES VS RIVETSPlexus adhesives have successfully replaced rivets in a variety of structural applications. The strength of a joint with rivets depends on the size of the rivet, the spacing of the rivet, and the gauge of the metal. The biggest challenge related to strength and durability with rivets is stress concentration. Drilling a hole through the material to place the rivet concentrates any loads experienced by the joint on that rivet.
SAVE TIME AND MONEY WHEN YOU SWITCH FROM RIVETS TO PLEXUS ADHESIVESTo see how using Plexus adhesives to bond metal to metal can save time and money, consider the following example.
MAKING THE SWITCH TO PLEXUS ADHESIVES
Before starting metal to metal bonding or using a metal bonding adhesive in general, there are a few important considerations:
I. What metal or other material will be bonded?
II. What surface preparation is required to get a good adhesive bond to metal?
III. How to bond metal with Plexus adhesives?
I. What metal or material will be bonded?
Plexus® Structural adhesives bond a variety of different metals including coated metals:
- Aluminum – Mill Finished
- Mild Steel
- Aluminum – Coil Coated
- Hot Dipped Galvanized (HDG)
- Aluminum – Anodized
- Electrogalvanized (EZG)
- Stainless Steel
- Aluminum – Extrusions
- E-Coated Metals
- Powder Coated Metals
Have a question about a specific grade of metal or coated metal to be glued? Take a look at our Adhesive Selector Guide or contact our technical service department via the contact on the right to have a test done.
II. Surface preparation
Several Plexus adhesives including the MA200, MA800, and MA8000 Series can bond metal to metal without a primer. The Plexus MA8000 series can even be used galvanized or zinc coated metal without primer.
However, some of the other adhesives in the Plexus portfolio require a Cleaner Conditioner called PC120. PC120 helps to clean the metal surface and improve strength of the bond over time. PC120 is dyed pink so that you can easily see where the metal has been properly cleaned.
Below is the typical surface preparation required to glue metal to metal:
|Surface||Typical Surface Preparation||Typical Surface Preparation|
|Type of Metal||Plexus® Primerless Adhesive||Plexus® Adhesive|
|Lightly Oxidized Metals||Dry Rag Wipe or Solvent Wipe||PC120 Cleaner Conditioner|
|Heavily Oxidized Metals||1. Solvent Wipe (IPA or Acetone)|
2. Sand or Grind
3. Solvent Wipe
|1. Solvent Wipe (IPA or Acetone)|
2. Sand or Grind
3. Solvent Wipe
|Coated Metals*||Dry Rag Wipe or Solvent Wipe||Dry Rag Wipe or Solvent Wipe|
*Testing needed to confirm adhesion to different coatings
Salt spray results using PC120 and Correct Amount to Use:
III. How to bond Metal with Plexus Adhesives
Plexus adhesives are 2-part (shortened to “2K”) adhesives that create a chemical reaction when mixing. The adhesives are typically mixed in a static mixer and dispensed unto on side. The two materials are mated together and then held in place until the adhesive has had time to cure or harden. This is often done by clamping. The adhesive continues to cure and once it has developed enough strength, the assembly can be unclamped.
Here are some key things to know:
- Working Time (also known as Open Time): The time elapsed between the moment Parts A and B of the adhesive system are combined and thoroughly mixed and the time when the adhesive is no longer useable.
- Fixture Time (also known as unclamp time): The time elapsed between the moment Parts A and B of the adhesive system are combined, thoroughly mixed and parts put together and the time when the assemble can be unclamped. This can change depending on the ambient temperature and temperature of the parts.
- Fixture strength: If the part needs to be lightly moved around, then 50 PSI might be enough strength. If the part will see higher loads after being put together, then 500 or 1000 PSI might be needed. Our Technical Service Department can help provide additional information. Get in touch with our technical service team via the contact form on the right.
BENEFITS OF BONDING METAL TO METAL WITH PLEXUS ADHESIVES
Strength and Durability of Plexus Adhesives on Metal to Metal Bonding
Proper usage of Plexus® Adhesives for bonding metals is expected to have significant advantages over traditional joining methods e.g. rivets, nuts, screws. Gluing a part can be a lot faster and can help speed up most assembly process. The continuous connections, strength and durability of adhesives may help to create a stronger structure than other joining methods.
Bonding Dissimilar Materials with plexus adhesives
Not only does Plexus® adhesives bond metal to metal, they are also often used to bond metal to composites and metal to thermoplastics.
For more information on bonding dissimilar substrates, get in touch with our technical services department via the form on the right.
ADHESIVE SELECTOR GUIDE
Looking to bond certain metal or coated metal? See our adheshive selector guide here.
If you have any questions about our adhesives or a project you are working on, please don’t hesitate to contact our technical service team.