How to Braze an Aluminum Bumper

In this video, an aluminum bumper reinforcement with a 7-inch cut is repaired with Super Alloy 5 and an oxyacetylene torch. Oxyacetylene is required for this repair, since the aluminum part is large and dissipates quickly. The aluminum bumper reinforcement must maintain a minimum of 800°F (more heat required due to thickness) throughout the entire repair to properly bond the Super Alloy 5 to the parent metal.

What is an Aluminum Bumper Reinforcement

A bumper reinforcement is a solid aluminum bar that reduces the impact of a collision by absorbing force and providing a cushion to the front and rear bumpers of a car. Bumper reinforcements or bumper bars primarily function to keep the internal engine parts safe in case of accident. Replacement parts can cost as much as $2500, so brazing these expensive parts with Super Alloy 5 can be the most cost-effective solution.

Note: Never braze a bumper reinforcement that has been bent or damaged. This video features a bumper bar with a cut that is easily repaired.

Aluminum Bumper Repair Process

Begin by using a Dremel tool or grinder to bevel the entire length of the crack. This step creates a groove which allows Super Alloy 5 to adhere to the parent metal.
Next, broadly heat the aluminum bumper reinforcement to slowly bring the part to the proper working temperature.
Briefly heat the end of the rod and dip it into the powder flux, then apply to the repair area.
Watch the flux. When it changes from powder to a clear liquid, this is the indication the parent metal has reached the proper working temperature.
Add the rod at the end of the crack and continue alternating adding rod and flux to fill the entire crack. If the rod begins to ball up, the parent metal has cooled too much. Simply discard the balled up portion, reheat the bumper reinforcement and try again.
Add more flux, if necessary, to improve flow.
Allow the part to cool naturally, and remove any excess flux with warm water and a wire brush.

Tips

Always keep the flux bottle as close as possible to the repair area, because aluminum drops 100°F per second.
Notice the technique: As soon as the rod began to flow, the heat is removed very quickly to avoid overheating the base metal.
If the flux turns black, you’ve applied too much heat. Remove it with water and a wire brush, re-prep the metal, and begin again.

Disclaimer

Please visit https://www.aws.org/Standards-and-Publications/Free-Resources/#YourResources prior to using our welding products, and adhere to all AWS welding safety guidelines.

Further product safety information is available at https://muggyweld.com/safety-guidelines

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Updated 11/23/25