Bonding metal to wood, on the face of it, sounds easy, but it is one area that tends not to bond well as you would expect because these two materials behave in such different ways. Moisture and temperature cause wood to swell or shrink. Compared to metal, which barely moves at all, but it can flex and vibrate, and heat up in the sun. A too-stiff adhesive could cause a joint to crack or flop over time.
1) Start with the right prep
Prepare the metal: Degrease to remove oil, polish, and fingerprints (nothing that leaves a residue).
Key the metal: Lightly scuff to add a “tooth” for adhesive.
Prep the wood – dry and dust-free. If the wood is somewhat wet, then that bond will be green, and it could pull apart as it dries. For Metal bonding adhesive, contact www.ct1.com/product-applications/metal-to-metal-adhesive
2) Selecting a rubbery background adhesive
This is why a flexible adhesive/sealant (usually either a polyurethane or hybrid polymer) will work better than any brittle glue for most metal-to-wood jobs. Flexibility allows the bond to deal with seasonal movement, vibration, and small gaps.
Indoor projects that are relatively stable can work with a two-part epoxy; for outdoor projects, this is more complicated unless specifically designed to allow movement and moisture.
3) Clamp smart, not hard
Squeeze the parts together, but do not squeeze all of the adhesive out. Make sure to follow the cure time of the product, and do not load any joint until it is fully cured.
Quick checklist
Keep wood dry
Roughen metal
Use an elastic adhesive for outdoor or moving joints.
As a rule, wait for the full cure of the adhesive before subjecting it to stress.
