Bonding metals securely:
Why pretreatment is crucial
What is this about?
Metals are among the more challenging substrates in wood construction and carpentry. Depending on the alloy, surfaces, oxidation behavior, and adhesion properties can vary significantly. A durable bond is therefore achieved not only by choosing the right adhesive, but above all through proper surface preparation.
Proper surface preparation and cleaning are key factors in determining whether a bond will hold up over time.
Typical metal applications
- Sandwich panels for tables, doors, gates, furniture, etc.
- Special alloys made of steel, copper, brass, tin, precious metals, etc., bonded to wood-based materials for interior design
- Facade elements
- Window sills
- Commercial kitchens
- Wall and ceiling elements
What is the challenge?
Metals differ greatly in terms of:
- Surface texture
- Oxidation behavior
- Strength and formability
- Adhesion properties
In addition, there are contaminants such as grease, release agents, or residues from protective films. Even thin oxide layers can weaken the bond and create a predetermined breaking point.
Common mistakes in practice
- Dirty surfaces are bonded directly.
- Oxide layers are not removed.
- The surface is not cleaned thoroughly after sanding.
- Too much time elapses between cleaning and bonding.
- The adhesive is selected without considering the loads it will be subjected to.
Here's how to do it
1. Inspect and clean the surface
Every surface should initially be considered contaminated.
- Remove oxide layers
- Remove grease and release agents
- Clean with clean ethanol or Collano HP 3100
- Change the cleaning cloth regularly
- Clean until no residue is visible
2. Sand only when necessary
Grinding is not a standard process.
- Sand only if oxide layers or coating residues need to be removed.
- Clean thoroughly afterward.
- Perform the bonding on the same day if possible.
3. Analyze requirements
The following questions are crucial:
- Indoor or outdoor use?
- Temperature exposure?
- Exposure to moisture?
- Mechanical stress?
- Differences in material expansion?
4. Choose an adhesive
The choice of adhesive depends on:
- Material combination
- Application method
- Load capacity
- Adhesion profile according to the technical data sheet
Field trials are always recommended.
Dos & Don'ts
Do
- Removing oxide layers
- Creating clean surfaces
- Analyzing requirements
- Conducting field tests
Don't
- Bonding to dirty surfaces
- Unnecessary sanding
- Allowing days to pass between cleaning and bonding
- Choosing an adhesive based on the "one-size-fits-all" principle
Key point: It’s not the adhesive that makes bonding metal difficult, it’s the surface. Metals must always be cleaned.
When should you get tested or seek advice?
Whenever:
- Des métaux différents sont combinés
- Des contraintes liées à des températures élevées ou à l'humidité sont présentes
- Des revêtements inconnus sont présents
