- Island cars live in salty, damp air, and many are parked near the sea. Rust usually shows underneath first.
- Surface rust on an older car is normal. Flaking, bubbling paint and anything you can push a finger through are not.
- Read the MOT history: the same corrosion advisory two years running means it's getting worse.
- Take a torch and a mat. Ten minutes on your knees can save you hundreds of pounds.
Nowhere on the Isle of Wight is more than a few miles from the sea. Salt spray carries inland on the wind, it settles on cars parked along the seafronts in Ryde, Sandown, Shanklin and Cowes, and in winter the roads are gritted with salt too. Salt and damp together speed up rust, so an island car can look tidy on top and be tired underneath.
That doesn't mean island cars are bad buys. It means rust is the first thing to check, before you fall for the colour or the spec.
Why salt air matters
Rust is iron reacting with oxygen and water. Salt makes the water conduct better, which speeds the reaction up, and it keeps surfaces damp for longer. Car makers protect the underside with coatings and wax, but stone chips, kerbs and age wear them away. Once water and salt get behind the coating, rust can spread underneath it where you can't see it.
Where to look
Take a torch, and something to kneel on. Look at the car cold and dry, in daylight. Start with the places water and salt collect.
- SillsRun your hand along the bottom edge under each door. Bubbling paint here usually means rust coming through from the inside.
- Wheel archesLook at the lip and the inner edge with a torch. Fresh underseal or thick paint in just one place can be hiding a repair.
- Subframes and suspension mountsHeavy flaking where the suspension bolts on is serious. These are structural parts.
- Brake pipesThey should look smooth. Pitted or swollen pipes need replacing, and the MOT tester will fail them if they're bad.
- Boot floor and spare wheel wellLift the carpet. Standing water or rust here means a leak.
- Door bottoms and tailgate edgesOpen them and check the bottom seams. Drain holes block and rust starts from inside.
How bad is too bad?
Almost every car over about eight years old has some rust underneath. What matters is the type and where it is.
What the MOT history tells you
MOT testers check structure and key parts for corrosion and fail a car where it has seriously weakened the metal, especially within 30cm of where things like brakes, steering and suspension are mounted. When it isn't bad enough to fail, they often note it as an advisory. Advisories are free to read on GOV.UK, and on car pages here when we have the registration.
Corrosion advisories usually read something like:
| What it says | What it means |
|---|---|
| “slightly corroded” | Normal for the car's age. Keep an eye on it. |
| “corroded but not seriously weakened” | The tester noticed it and wrote it down. Look at it yourself and ask what's been done. |
| Corrosion on brake pipes | Pipes are cheap-ish to replace, but they will need doing. Budget for it. |
| The same advisory, two or more years running | It hasn't been fixed and it's getting worse. Expect it to fail soon. |
| A fail for “excessively corroded”, then a pass | It was repaired. Ask for the invoice: a proper welded repair is fine. |
The guide to reading an MOT history covers the rest of the record, including mileage.
Which cars cope best?
Modern cars are far better protected than those of twenty years ago, and most mainstream makes now use galvanised steel for the body. Age and how a car has been kept matter more than the badge. As a rough guide:
- Under about six years old: rust is rare. Look for stone chips and accident repairs instead.
- Six to twelve years: expect some surface rust underneath. Focus on brake pipes, subframes and arches.
- Over twelve years: check carefully, and price in some work. A well-kept older car can still be a good buy.
Looking after it once it's yours
- Wash underneath now and then, especially after winter and if you park near the sea. A hose under the arches and sills helps.
- Fix stone chips before they rust. A touch-up pen is cheap.
- Keep drain holes clear in the doors, sills and around the scuttle under the windscreen.
- Consider a cavity wax or underbody treatment on an older car you plan to keep. Ask a local garage for a price.
When we have the registration, you'll see every advisory before you go.
