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Homepage. This page: Locating corrosion on classic cars, plus advice on rust prevention and cure when you find it.

Rust, and the classic car.

Rust is probably the principal killer of most normal (ie mild steel) bodied cars. Peruse the cars stacked up in a scrapyard and many aren't there through being worn out mechanically, it's often through terminal tin worm. Even fairly modern cars suffer from structural corrosion, despite them having better rust protection than the cars that typically fall under the "classic" title. Wander around your favourite breakers yard (if this kind of activity is still permitted), and for every hundred or so cars at rest, there may be ten to twenty examples that are there through having been in a crash, a similar number which are tired mechanically, and the remainder there due to electronic failings, or levels of corrosion that render them beyond economical repair.
The tricky part with preventing serious rust corrosion is spotting it early enough to do something about it. Corrosion may have been caused by flying stones or minor impact damage, and as such is easy to spot and hopefully address before it takes a real hold. Problems grow significantly when the rot has worked its way from within, often starting in box sections or double-skinned rust traps where panels join together. Rust can munch away at steel at an alarming rate ('rust never sleeps' is a mantra that was drilled into me many moons ago by a MIG-wielding friend), and where it has worked its way to the surface, you'll often find a catalogue of horrors beneath, where the rot has been left unchecked. A few innocent bubbles therefore on the surface could herald a sea of rot below the surface, out of sight.
Rusty Austin A40 car
Hard to believe that this rusty wreck was once a glistening, shiny new Austin A40.
Some years ago we owned what looked like a very well preserved example of mid-1980s Escort Ghia, ok not the type of car to keep you awake at night in anticipation of driving, but a presentable runabout nonetheless. Unusually, there was no visible rot, so we were fairly confident that it'd last us a few years. With the MOT looming, I decided to jack it up and have a quick shufty underneath ... which was when my joy at owning a supposedly rot-free Ford dissipated when I saw the rotten box sections around the back end of the floor area, and some ominously frilly bits of steel in the footwells. Hence our disposal of an outwardly presentable motor car for a miserly 30 quid, and this on a car that was only 15 years old and supposedly better built than cars of yesteryear. Part of the problem with many moderns is that the gauge of steel used is often quite thin, so once rust does get a hold, such as on our Escort, it takes very little time for it to perforate the gleaming bodywork, whereas on an older classic car the metal used is often thicker and more resilient to the never-ending onslaught of the grot once it has taken hold.

Helping to preventing rust.

The best way to minimise the aggravation caused by rust is to buy a good clean example of a classic car in the first place, assuming that you are planning to buy a runner, as opposed to a rusty old wreck as a project car, and keep it in fine fettle. I can only speak about motorists in the UK, saddled as we are with alarmingly damp weather for much of the year. A bone-dry de-humidified garage is favourite when it comes to preserving your classic or vintage vehicle, but sadly most of us can only dream about such an option. A good compromise in many ways is a car port alongside the house, as this keeps the worst of the elements off your car, and importantly allows for good ventilation. In fact if a 1960s Austin Mini or Ford Cortina is your daily car, and it's dripping wet following a shower of rain, it will be better off being parked in a well ventilated car port than locked away in a stuffy garage, as the through ventilation in the carport will help dry the car off far more effectively than parking your soaking wet classic in the garage.
Worse still is covering the car with a plastic sheet, especially if the car is damp. All that happens is that moisture gets trapped under the sheet, and doesn't let the car breath - even so-called breathable car covers are at best a compromise I've found. If you really want your classic to fall apart through corrosion, then park it on long grass with a plastic sheet strapped over it. The grass will stay damp for ages, and come the next warm day, the moisture will escape from the green stuff and settle on both the top and underside of your car, being trapped there by the plastic sheet that allows for no ventilation or moisture release.
Old MG under a cover
A tattered old cover won't have done this vintage MG, parked in long grass, any favours.
If your car must live outside, it's essential that the screen seals are operating effectively, as water leaking into the footwells can wreak havoc with floorpans, sills, door pillars and so on. Carpet, and under-carpet soundproofing material, absorbs moisture very effectively, trapping it against your car's steel floorpans, rarely drying out fully even after a dry spell of weather. Quite often tracking down where the water is ingressing can be a tedious and frustrating business. Areas worth checking that may not spring to mind immediately include sunroof drain channels (where fitted), windscreen wiper spindle grommets (where the wiper spindles stick out through the bodywork, are the rubber seals still ok?), leaking heater (or air con) pipework under the dashboard, missing rubber grommets in the floorpan itself, poor welding repairs that are letting water in at the seams, roof mounted aerials that are not sealed properly, door seals (have they flattened and lost their compliance through old age?) and last but not least, rot in the bulkhead, including the battery tray, which can often be very difficult to spot and even to repair properly.
So as already mentioned, prevention is 100% better than cure, and if at all possible try to buy the best example of classic car you can, one that isn't already riddled with rust (unless you get a kick out of MIG welding). A major cause of rust is through the build up of mud in inaccessible areas underneath, such as around suspension pick-up points, wheel arch lips, behind headlamp bowls where mud easily gets trapped, and sills. Mud, once dampened, can stay that way for days following a rain shower, and just like interior carpets, harbours moisture very effectively. Wherever possible maintain the underside of your car in clean condition, underseal if you must, but keep it clean and free of any sludge buildup that will encourage and harbour damp. There are many waxy anti-rust solutions that can be sprayed or brushed onto the underside of your car, and equally into its many box sections. These can provide a very robust means of keeping damp at bay, although they do need repeat applications in areas such as wheelarches that get repeated blasting from road spray and grime. Waxoyl is one of the better known products, and one that I've used to good effect in the past. There are plenty of other products from companies such as Commer and Dinitrol, and any classic car magazine will have numerous advertisements for these rust-busting solutions.
Dampness therefore is certainly a pain, but there is an even greater threat to your classic's gleaming coachwork, if you happen to live in parts of the UK and other selected countries, and that is road salt! Local authorities launch droves of gritting vehicles at the merest hint of chilly weather, all aimed at ensuring that people who can't grasp driving in slippery icy conditions have half a chance of getting home in one piece, lowering as it does the freezing point of the snow & ice covered roads that it gets sprayed upon. This is all very well, but the slushy salt-laden cocktail that gets blasted around your cars structure is a highly corrosive mix, and accelerates the rusting process better than any other method. My first Triumph Spitfire ran on very nicely painted steel wheels, and looked the part all summer and autumn, but within a week of the first appearance of salt on the roads, they started rusting, as did the chromework, despite me hosing off this nasty brine whenever I could.
If you can, avoid taking your pride and joy out in such unpleasant conditions. If you rely on your classic for daily use, and use it throughout the winter, then ensure that the underside is kept as clean as possible (regular jet washes can help here) and either remove the rare chrome parts altogether, or liberally coat then with a hard wax polish and leave it in place - the finish might look a bit dull, but a quick wipe over with white spirit in the new year will see your chromework back to its usual glistening self, as opposed to pock marked and corroded thanks to the aforementioned salt. A chap who lives local to me acquired some road grit from a contact of his in the council, and used it to treat his concrete driveway one winter. Not long after, he noticed that the surface of the concrete had become pock-marked by the grit/salt mix, so if it can do this to concrete, imagine the destruction it can cause to the underside of a car.
Chevrolet in use on winter's roads
This 1950 Chevrolet saw use throughout the winter in its early years.
Re-chroming is a very expensive business, and if your car has a large number of Mazak mouldings (usually badges and grille ornaments) then replacement may be the only option, assuming you can find replacements, hence the importance of looking after what you have already got. If I ran a car on alloy or spoked wheels, I'd make sure that I had a slave set of normal steel wheels to drop on over winter, preserving the expensive wheels which can sit nice and snugly in the garage with a sheet over them til the spring.

Common rust areas.

Many classics have specific areas of corrosion that are unique to their design, and as such couldn't be covered in a general article like this. However there are several key locations on most steel-bodied cars that need close scrutiny, glassfibre and alloy bodied cars being out of scope here. I'll try to cover off the most popular areas to check over when viewing a prospective purchase, a panel at a time.
Front wings are probably the biggest single headache when it comes to rust and subsequent repair on classics. Unless you have deep pockets and a popular model (such as an MGB, Midget or Mini), replacement panels may take some hunting down.
The most common area for bodged repairs is around a car's headlights, this being a classic damp trap on many an old car, with mud getting trapped between the headlamp bowl and the outer wing itself, and regularly receiving a soaking whenever wet roads are encountered. Look for any hint of bubbling which will signify significant problems lurking below - rust is often x10 worse than that which is initially apparent, as I know to my cost. The front wing area immediately behind the roadwheels is another classic location for rust to take its hold, battered as it is by road dirt and spray - many classics have tinwork lurking in this area, cunning disguised to look good with a swathe of filler. Corroded areas "improved" with a coat of filler and paint may look presentable for a few months, but the rust WILL appear through the filler eventually, no matter how thickly it was ladled on, and by that time the problem will be far worse than before. Wherever there are trim strips or other bodywork adornments, there are further opportunities for moisture to get trapped and munch its way through the metal. My A40 has suffered from all these problems, there is bubbling around the headlamps, bubbling along the wing where the stainless trims is attached, and behind the front wheels, accelerating rust into the sills behind.
Front end panels can suffer too, these often comprise a number of smaller panels joined together, leading to plenty of rust trap possibilities, which are often hidden from sight by radiators, grills, bumpers and so on. Bonnets rarely suffer from terminal rot, as the worst panels for suffering are those along the lower edges of the bodywork, for obvious reasons, although its not unknown for certain models to suffer rusty bonnets if their particular design lends itself to trapping moisture.
The frame around and below the windscreen, the lower part attaching to the top of the bulkhead, can suffer extensive corrosion if the screen seals leak, or if the air vent which can often be located below the screen has been allowed to fill up with rotten leaves, flies etc and attract damp over time. Corrosion around rear screens isn't unknown on many cars either, and would require the screen to be removed before an effective repair can be made. You'd need to ensure that new screen seals are available for that particular car too before embarking on this not-insignificant repair.
Rusty Volvo
This Volvo demonstrates many of the common rot zones on a typical classic car.
Rust bubbling around the screen(s) can be a pig to repair properly, often requiring much of the dashboard to be removed, along with various underbonnet components, to gain sufficient access to make a repair. Minis for example are notorious for rotting in these areas, not least because they were often run as a cheap runaround, whose owners were either unable or not prepared to invest in time-consuming and expensive repair operations, more often than not slapping on a wedge of filler and hoping for the best.
Moving further back, we have the A post, which usually carries the front door hinges and is a key structural member between the top of the scuttle (bulkhead) and the floorpans and sills below. Any damage here can cause doors to not open & close correctly - look for paintwork damage and uneven panel gaps around the doors - and can be tricky to fix properly, rotting as they often do, from the bottom up. If there is serious A post rot, you can be sure that the nearby footwells are equally on their way out, and the sills (which often comprise a number of separate pressings to give them strength) are beginning to go the same way.
Sills and floorpans can take a real battering, and on most monocoque (unibody) cars they are structural. The Triumph Spitfire is a classic example of a car which can suffer more than most if the sills are shot. Despite having a separate chassis, the Spit still relies on bodywork (sills) for structural strength, especially given thats it's a convertible and doesn't have a permanent steel roof to provide structural rigidity. Rare is the Spitfire that hasn't needed sill and floorpan welding by now, given that the youngest is over 30 years old now. The main giveaway that all is not well is when the doors start to droop, or when the doors are lifted upon slightly, the whole A post moves in unison with the door (don't confuse movement here with worn door hinges however). Floorpans and sills are often candidates for hasty MOT repairs, where often the correct method of cutting out the rotten area before welding in new steel is conveniently overlooked, and new metal just gets tacked over the rot to temporarily disguise the real problems below. Therefore it is critical to assess the condition of the floorpan from both above and below, as it's not unusual to find patches 3 or 4 deep in the worst affected areas.
The doors themselves are often less of a headache, simply because usually they are easy to unbolt and replace. Rot is usually confined to the lower edges of the door skin, probably through poor door-to-window sealing, and blocked drain holes. If the doors have been left to rust for many years, it's very likely that the door frames will also have suffered, making repair a lot more involved. With a popular car such as a Jaguar or a Ford, sourcing a better replacement door is often the easiest route to take, although if your car is pre-war or particularly unusual, replacements may be scarce so repair may be the only option available.
Fortunately the roof panel of a saloon car rarely gives trouble, although as with all things there are exceptions (have a look at this rusty Ford Model Y as a good example!). A small number of vehicles, including the Morris Minor van for instance, can suffer serious rot around the roof gutters, while De Tomasos from the 1970s have been known to rot above the rear window.
Moving rearwards once again, the back arches are vulnerable on just about any car. As with the front wings, these suffer at the hands of the elements, and often have double skinning which, if damp get trapped inside, can wreak havoc - just take a look at any Series 1,2 or 3 XJ Jaguar, look carefully at the rear arches, chances are they've had new metal let in. Inspect them closely therefore, and don't be surprised to find them cunningly stuffed with filler in an attempt to make them look ok. And while you're at it, stick your head (carefully) underneath and inspect the rear end of the sills, outriggers and floorpans for grot, especially as suspension pick-up points can be found in these areas (XJ6, Mk2 GT6 etc), and add extra strain to those areas of panelwork.
Rusty Vanden Plas 4 Litre R
The bootlid on this Vanden Plas is perhaps the least rusty panel on the entire car.
Open the bootlid and lift any carpets that are in there, and inspect for any corrosion in the far corners where the inner rear arches join the boot floor, and along all of the edges of the boot floor, using a torch if necessary. The bootlid itself can rot as much as anywhere else, but as with the doors and bonnet at least they are usually bolted on and therefore not too tricky to replace. Condensation, forming on the inside of the bootlid and dripping down into the lower lip of the bootlid panel, can be a problem with some cars.
Wherever rust is found, replacement of the metal is nearly always the best long-term repair. Rust preventers and converters can help, but a lot depends on how closely the usage instructions are followed, and how well the car is looked after later on. I've rarely had much luck with rust converters, but they're worth a try if the corrosion isn't yet too advanced.
If you are going to look at a classic for the first time, you can print off a one-page checklist describing all the common areas in which cars can rust - just visit the free stuff page to find out more. A separate article, describing ways to remove nuts and bolts on cars that have rusted up tight, may also be of interest - you can read that article on dealing with corroded nuts here.
Diagram showing common rot spots

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