Aluminium bodywork: what changes when it's repaired

A few years ago, aluminium bodywork was mostly found on high-end cars. Today it is common on bonnets, tailgates, wings, doors and reinforcements on many everyday models. Manufacturers use it because it weighs considerably less than steel and stands up well to the weather. But when it comes to repairs, it is not worked in the same way.

How to tell if a panel is aluminium

The simplest way is with a magnet: aluminium is not magnetic, so the magnet will not stick. If you are not sure which panels on your car are aluminium, we check before preparing the quote, because it affects the repair method and the time involved.

A metal with its own character

• It has less ‘memory’. Steel tends to spring back to shape when straightened. Aluminium less so, and it hardens as it is worked cold, so it can crack if forced. It is often worked with controlled heat.
• It is softer. It marks easily, which means tools and supports must be in good condition.
• It conducts heat very well. That changes how it is welded and heated, and temperatures need closer control.
• It is joined differently. On many aluminium bodies, panels are not welded but joined with rivets and structural adhesives, following the manufacturer's instructions.

The big enemy: galvanic corrosion

Aluminium does not rust the way steel does, with the familiar reddish flakes, but it has its own weak spot. When it touches another metal such as steel and there is moisture present, a tiny corrosion cell forms and one of the two metals is gradually eaten away. This is galvanic corrosion, and in that pairing it is the aluminium that loses.

That is why joints between aluminium and steel parts use specially treated rivets, adhesives and sealers that insulate one metal from the other. It is also why leaving steel dust or swarf on aluminium is a bad idea: those embedded particles can start small spots of corrosion under the paint.

Why it's worked separately

To avoid that contamination, aluminium should be worked with its own tools: sanders, discs, brushes and hammers that have never touched steel. Ideally there is a reserved area or set of equipment with its own extraction, because aluminium dust also calls for safety precautions. It is a detail you never see, but it makes a real difference to how the repair ages.

Joining aluminium panels

When a panel or part of one needs replacing, the factory joining method is reproduced. Often that is riveting combined with structural adhesive, which spreads the loads, seals the joint and insulates the materials. Before bonding, surfaces must be perfectly clean, dry and prepared; any trace of grease or moisture reduces adhesion.

Painting aluminium

Aluminium needs adapted surface preparation: primers that bond well to this metal and careful cleaning, because on contact with air it quickly forms a surface layer that makes adhesion harder. From there, painting follows the same process as any other panel.

Is the repair more expensive?

Sometimes a little, because it takes more time, specific tools and extra care at every stage. In return, properly repaired aluminium does not suffer the typical rusting of steel and keeps the lightness the manufacturer designed in. What you should avoid is treating it like steel to save money: a repair like that can crack or corrode before long, and then it works out far more expensive.

If your car has damage on an aluminium panel, get in touch. You can see how we handle panel repair and chassis jig and structural work, or simply ask for a quote.