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Figure 1 - The bodyline area of this aluminum fender may be difficult to straighten due to the work hardening effect.

Figure 2 - The crack in this aluminum hood will be welded following hammer and dolly work.

Figure 3 - A very common type of collision damage is rear door and quarter panel dogleg damage.

Figure 4 - There are no recommendations for or against sectioning an aluminum quarter panel through the dogleg area of this vehicle. How would you proceed with this repair?

ALUMINUM EXTERIOR PANELS, REPAIR OR REPLACE?

As collision technicians and estimators, we have all become accustomed to the idea of encountering an aluminum exterior body panel during the damage analysis process. The question often arises whether to repair or replace a damaged aluminum exterior panel? In some instances the answer may be quite simple, while other times it may be more challenging to make a decision. Let’s take a look at some of the more challenging scenarios and considerations to keep in mind.

Scenario 1: Size and Location of the Damage

Repairing mild steel body panels with collision damage is nothing new. Using hammers, dollies, and picks when access to the backside is obtainable is a very common practice for straightening. With areas of limited access to the backside, using a weld-on dent puller for straightening is also quite common. So why does this change when dealing with an aluminum exterior panel?

The first factor to think about is that steel has memory, aluminum does not. A damaged aluminum panel will not remember that it was a previous shape. An aluminum panel that has been reshaped due to collision forces will take on a new shape and forget the old shape.

The next factor is that when this reshaping occurs, the aluminum panel will also undergo some work hardening. Work hardening is strengthening through shaping. Typically, the more the damage that there is, the more work hardening that takes place. So not only did the aluminum panel get damaged, but it got stronger.

When considering these factors, the size of the damage becomes a consideration. A repair that can be done on a steel door with a large crease may not be feasible on an aluminum door with similar damage. Location is another consideration. Small damage with backside access may be quite easily repaired on an aluminum panel. What if the damage is on a bodyline or crown? Bodylines and crowns not only enhance the appearance of a vehicle, they strengthen the panel. These areas have already been work hardened once during the initial stamping process. Collision damage has now work-hardened these areas again, strengthening them even more (see Figure 1). Small damage in areas such as this may offer high resistance to straightening.

What if the damage is not accessible from the backside? Weld-on dent pulling equipment used for steel panels will not work for aluminum panels. There are aluminum-specific weld-on dent pulling tools available from some equipment makers. There are also glue-on dent pulling tools available that can be used on smaller sized damaged panels. The I-CAR Straightening Aluminum Panels (STA01) training program contains information on techniques for using these types of tools for straightening.

Scenario 2: Cracked Panels

If there is a crack in a damaged aluminum exterior panel, the area around the crack has work hardened to the point of becoming very brittle, which caused the panel to crack. Can the crack be welded and the panel repaired? Some vehicle makers warn against repairing cracked aluminum exterior panels. Examples include Acura, Audi, Honda, and Jaguar. All of these vehicle makers recommend that aluminum exterior body panels be replaced if cracked. If not following vehicle maker recommendations, all parties pertaining to the repair should be consulted and involved in the final decision on how repairs will proceed.

Other vehicle makers say it is acceptable to repair cracked aluminum exterior body panels by welding (see Figure 2). This will require the repair facility to have a welding machine capable of welding aluminum. Depending on where the crack is located, it may be very difficult to clean both sides of the weld joint to obtain a good, solid weld. Also, the part that will be welded may also need to be removed from the vehicle to allow for weld dressing, cosmetic repair, and jamb refinishing.

Scenario 3: “Dogleg” Dilemma

Imagine an Audi A8 or a Jaguar XJ. These are both four-door sedans, both with aluminum exterior body panels and an aluminum structure. The vehicle has collision damage on the back door and the dogleg of the quarter panel. The door is a bolted-on part and will be replaced. The damage to the dogleg is a very sharp crease that has deformed the inner portion of the jamb, but there is no crack in the panel (see Figure 3). There are three possible ways to approach this type of damage along with considerations for each.

Straightening can be considered. Using a weld-on dent puller for aluminum, it may be possible to pull out the damaged area of the dogleg. The dogleg section of a quarter panel is a very highly formed stamped part, so it is very strong from work hardening already. It may be necessary for one technician to be warming the area while a second technician uses the dent pulling tool. The area may crack from the straightening attempts, if not done in a gradual, controlled manner.

Full panel replacement is also a consideration. This will require all the standard operations of replacing a quarter panel, such as removing the backglass. Full panel replacement will also require separating all of the factory joints for a very small, damaged section of panel. This is a common repair in this instance (see Figure 4).

Partial panel replacement would be the third consideration. There are no procedures for dogleg sectioning of an Audi A8 or Jaguar XJ. There is also no recommendation against doing such a repair. A partial replacement may be possible, similar to doing a steel dogleg, with the proper equipment and repair practices. This would again be an instance where all parties pertaining to the repair should be consulted and involved in the final decision on how repairs will proceed.

Final Analysis

Damage analysis on any type of vehicle, whether steel or aluminum, can be challenging in making repair versus replace decisions. With aluminum being used more and more, we need to be aware that some repairs may not be the same as on a steel vehicle, but we do not need to abandon all of our past experiences to help us come up with the best solutions.

The topics discussed here are merely considerations for the next time you are analyzing damage on a vehicle where the magnet will not stick, and you are faced with the age old question, repair or replace?



For comments or suggestions on the Advantage Online, please contact I-CAR Senior Instructional Designer Bob Jansen at bob.jansen@i-car.com.

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