Cosmetic Repairs To Aluminum Exterior Panels

The bodyline area of this aluminum fender may be difficult to straighten due to the work hardening effect. (Photo Courtesy of Jaguar)

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 and suction cup types of dent pulling tools available.

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