Rivet bonding – the use of rivets combined with structural adhesives to join panels – is very common among heavy duty truck OEMs. Most truck manufacturers use rivet bonding on side and back panels, front hood closures, headliners and many inter-structural reinforcements of the cab designs. However, technicians in collision repair may lack the training and information for professional repairs that require rivet bonding.
About rivet repairs
There are several factors to consider when repairing with rivets. Rivets alone are great for holding panels together in the shop; but with movement and vibration, fatigue and corrosion can result, leading to panel bond failures. When it comes to dissimilar substrates, the laws of physics work against us: for example, when an aluminum panel comes into contact with a steel rivet, galvanic corrosion can easily occur. If the joint is not properly sealed, an electrolyte such as an acid, moisture or road salt can quickly start the corrosion process.
Heavy duty truck OEMs can apply anti-corrosion coatings on aluminum and other metal panels where the rivets attach. However, the technician may remove this corrosion protection during panel removal or surface preparation, leaving bare metal exposed. Sometimes, these panels may get riveted back together without the corrosion protection restored. This can result in a compromised repair – and a mark on the reputation of the repair facility. Working with aluminum also requires special precautions related to worker safety and substrate preparation, as well as proper process mapping and site and workplace hygiene. Use OEM and vendor information to help educate yourself on best practices when working with aluminum and mixed metal repairs. Follow these recommendations diligently; even a small deviation or missed step in the process can cause a repair failure.
The use of an adhesive such as 3M PN8115 Panel Bonding Adhesive in addition to rivets when performing a repair can result in higher bond strength versus rivets alone. It can also provide leak prevention, reduced rivet vibration and lower point stress which can reduce fatigue and cracks. Just as importantly, the adhesive can also serve as an isolator between dissimilar metals – an excellent way to reduce the potential for corrosion.
The process of rivet bonding with adhesives
In this process, the adhesive is being used as a bonder and as an isolator
- Straighten the host panel mating flange on the truck to ensure proper fit-up of the service part.
- If using rivets that require drilling: clamp the panels, drill the holes and deburr the drilled holes as needed.
- Clean with an approved low-VOC compliant surface cleaner on the truck body and the service part.
- Sand the mating flanges on the truck and the service part using a 3M 80 grade abrasive and a dual action sander. (Remember, on aluminum the surface needs to coated within one hour to avoid surface oxidation.)
- Re-clean both surfaces with an approved low-VOC wax and grease remover.
- Apply a thin bead of adhesive to the mating flange(s). Using a filler spreader or acid brush, cover bare metal on the mating flange completely.
- Apply a second bead of adhesive to achieve adequate bond-line thickness, and clamp the part into place. Apply a thin coat of adhesive on the edges of the drilled holes to cover exposed metal before inserting rivets.
- Apply a second bead of adhesive to achieve adequate bond-line thickness, and clamp the part into place.
- Install the proper rivet recommended by the OEM.
- Remove the clamps. Remove excess squeeze-out before the adhesive cures, as grinding cured adhesive can create corrosion hot spots and collateral damage.
Visit 3MCollision.com and select “Heavy Duty Truck” under the “Products” or “Applications” tab to help you choose the correct adhesive for your repair.