Rust protection after a bodywork repair

When a car leaves the factory, its body has several barriers against corrosion: the steel is usually galvanised, the whole body is dipped in a cathodic e-coat, seams are sealed and internal cavities receive protective wax. A collision and its repair break some of those barriers. If they are not rebuilt at the end, rust appears sooner or later, often somewhere you cannot see until it is too late.

In southern Tenerife, with the salt and humidity of the sea air, the risk is even greater. So rust protection is not an extra: it is part of doing the repair properly.

What breaks the factory protection

• Sanding. Repairs mean removing paint and sometimes going down to bare metal.
• Welding heat. It burns off the galvanising and e-coat around the joint, on both sides.
• Replacing panels. Cutting and joining panels opens up seams and inner surfaces that were previously protected.
• Panel work. Straightening a panel can crack the protective layers on its inner face.

The tools against rust

Several products are designed to restore that protection, each for a different area:

• Anti-corrosion primers. Applied to bare metal before filling or painting. They protect the steel and improve adhesion of the layers that follow.
• Cold galvanising. A zinc-rich compound applied where welding or heat has destroyed the original galvanising, giving the steel protection similar to the factory's.
• Cavity wax. A fluid product sprayed through a long lance inside sills, box sections, doors and closed cavities. It creeps into small corners and forms a film that keeps moisture off the metal.
• Stone-chip coating and underbody protection. A textured coating applied to the underside, sills and wheel arches to absorb the impact of stones and grit that would otherwise chip the paint down to the metal.
• Seam sealers. They close the joints between panels so water cannot get into the overlaps, which is where rust most easily starts.

Order matters

These products are not applied all at once or just anywhere. Protection that goes between two overlapping panels has to go on before they are joined, and it must withstand welding heat without breaking down. Primer goes on before filler. Sealer and stone-chip coating are applied before the top coat, so they end up body colour. And cavity wax is sprayed at the very end, once there will be no more heat or paint in that area.

Out of sight, once again

Almost all of this protection ends up hidden: inside a door, under a sill or between two panels. That is why a rushed repair can easily skip it, and the car leaves the workshop looking perfect. The problem shows up a year or two later, as bubbles in the paint near a seam or rust peeping out along the bottom edge of a door.

Corrosion starts from the inside. Protection has to reach the inside too.

What you can do

• Ask the workshop whether the repair includes anti-corrosion treatment on welded areas and inside cavities.
• If you live near the coast, rinse the underside of the car with fresh water now and then to remove salt.
• Do not leave chips that reach bare metal untreated, especially on the lower part of the car.

If you want to protect your car, or think an old repair is starting to rust, have a look at our rust protection treatment or ask for a quote. We will check it and tell you what it needs.