How to Identify Rust When Buying a Classic Car
Rust kills more classic cars than any mechanical failure. Learn to spot warning signs and hidden problems before they become expensive surprises.
James Park
Technical Editor
Mechanical problems can usually be fixed. Electrical gremlins can be traced. But rust — rust is the cancer of classic cars. Left unchecked, it spreads until repair costs exceed the vehicle's value.
At BetterQA, we test software by methodically checking every potential failure point. This guide applies the same systematic approach to rust inspection — because the problems you miss are the ones that cost you.
The Three Types of Rust
Surface Rust
Cosmetic only — affects the paint layer and very top of the steel. Easily treated with sanding and proper preparation.
Scale Rust
Progressed deeper into the steel. The metal surface is pitted and rough. Can be treated but requires more aggressive intervention.
Penetrating Rust
Through the steel. Holes form, structural members weaken. Repair means cutting out and welding in new metal. Expensive.
Where to Look: The Usual Suspects
Sills (Rocker Panels)
Poke firmly with a screwdriver at the base of the sill. Sound metal resists; rotten metal crumbles. Look for bubbling paint or fresh underseal.
Wheel Arches
Feel inside the arch with your hand. Compare both sides — asymmetry suggests repair or ongoing problems.
Floor Pans
Lift all carpets and sound deadening. Poke suspected areas. Fresh underseal is a red flag.
Door Bottoms
Run your finger along the bottom edge. Feel for roughness or thin spots.
Boot (Trunk) Floor
Remove all contents and liners. Check particularly around the edges.
Red Flags: Signs of Hidden Problems
- Fresh underseal: Often applied to hide problems
- Paint bubbling: Rust pushing from underneath
- Misaligned panels: May indicate rust in structural areas
- Evidence of filler: Use a magnet to check panels
- New carpets in old cars: Why were they replaced?
Pre-Purchase Inspection is Worth It
For any classic car over €10,000, a professional pre-purchase inspection pays for itself. Expect to pay €200-400, but that's cheap compared to discovering €5,000 of hidden rust after you've bought the car.
On Finds, we encourage sellers to provide detailed photos of known problem areas and disclose previous repairs.
Finds is built by BetterQA. We believe in transparency — sellers must disclose known issues.
James Park
Technical Editor
James Park is Technical Editor at Finds, where he translates complex mechanical topics into accessible guidance for collectors. Finds is part of the BetterQA portfolio.
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Finds is part of the BetterQA family of quality-focused products · betterqa.co