Taking a closer look at bonding, riveting and welding

Nov. 4, 2019
With the increased use of aluminum, and the great difficulty of actually resistance welding aluminum, we have seen a surge in automotive rivet applications at the original equipment (OE) part level and in field repairs.

As the collision repair industry increasingly embraces original equipment manufacturer (OEM) repair procedures as the proper way to fix vehicles, many are asking “why” – why are things done a particular way and why are specific products and fasteners used? Many of these questions can only be answered by the OEM and are based on firsthand experience and past research. With a marketplace full of options for adhesives, rivets and even tooling to install the fasteners, it’s not uncommon to get overwhelmed. So, let’s first try to understand some of the “whys.”

“Approved” vs. “Recommended” – which is it? This is one of the more confusing topics for body shops. To an OEM, “approval” is a lengthy process of adhesive testing in which bond strength is just the beginning. From there, they explore how various environmental conditions and time affect the strength. Humidity, temperature, corrosion and even ultraviolet (UV) light can all change an adhesives strength or bond strength. This process is often called “spec testing” and follows a specific OEM standard, or standards, so it is repeatable and comparable data can be collected. These tests are a compilation that assist the OEM engineers in making a decision of equivalence. The entire approval testing process will generally take upwards of a year to complete, as some tests are lengthier.

Rivet bonding application on ATS/CTS using Fusor® 2098 Structural Adhesives.

“Recommended” labels are much simpler and usually based on engineering judgment of “equivalence.” Typically, you’ll see recommendations where the product or application is non-critical, such as a seam sealer. However, a structural adhesive in a crash critical area, like a rail or pillar, will always be highly tested before being referenced in a repair procedure – and never just recommended without testing and data.

Weld bonding, the process of combining adhesives and welding, has been a long-time repair solution for about 20 years now. With the increased use of aluminum, and the great difficulty of actually resistance welding aluminum, we have seen a surge in automotive rivet applications at the original equipment (OE) part level and in field repairs. For many years now, rivets have been commonly used in other applications (construction, aerospace, over the road trailers, etc.), but are now dramatically increasing in collision repairs. Structural “pull rivets” are far from new in collision repair – they have been used in recalls and service repairs on many vehicles because they require a much-reduced technical capability, as opposed to welding, to achieve a consistent and robust repair, while also requiring “simple” tools.

Rivet bonding application with Fusor® 208B panel bonding adhesive.

With self-piercing and flow-form rivets, along with the more complicated and costly tooling, becoming the norm in collision repair, there is much discussion around one standard question: “Do I really need to use the OEM fastener?” The answer is “yes.” Trying to reengineer the repair by using alternative fasteners is a recipe for disaster. Always follow the OEM repair procedures while using the specified fasteners and tooling – even using a “similar” rivet could become a problem. Something as simple as the OEM-specified coating not being on the fastener may lead to issues down the road.

The number one source for proper repair information is the OEM. While there are other sources for some OEM repair procedures, they all draw from the OEM – so, why not just go directly to the expert? OEM1STOP.com is the best starting point as it’s a simple launch pad to all OEM service information websites. Yes, all the OEMs charge for access to their service publications, and each site is different in use and navigation, but this is a requirement to obtain the most accurate information. Keep in mind that the service publications are “live” and updated constantly, so information saved from the last repair might have changed. Save procedures to your job folder for backup documentation for future reference only, but not for future repairs.

The constant fluctuation of equipment, fasteners, adhesives and procedures can be challenging, and sometimes frustrating, but this is the norm now. Our field requires continuous learning and training. We must remain agile as we adapt to new methods, equipment and consumables.

About the Author

Douglas Craig

Douglas Craig is the Structural Adhesives Applications Engineering Manager & Collision Repair Industry Liaison for LORD Corporation.

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