Rust has always been a problem for cars in the UK, caused by wet winters and salted roads.  

If your car is showing signs of rust, it's best to get it sorted as soon as possible, the longer it’s left the larger the bill will be. Read on to find out how much you can expect to pay for a rust repair cost for your car. 

What causes cars to rust in the UK? 

Rust is caused by the oxidation of the iron present in steel; the most common material for making car bodies and suspension components. Water and salt accelerate this process, and cars in the UK are subject to significant amounts of both.  

How much does rust cost to repair? 

Budget anywhere from £200 for a patch rust repair, to £3,000+ for multiple panel replacement.  

However, the exact cost depends on the area, type of car, and extent of the rust.  

We’ve listed some common rust areas, their causes, and costs below. 

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What are the most common areas to rust? 

With cars being all different shapes and designs, rust doesn’t always appear in the same place. Here are some common areas you might find rust, and how to spot them. 

Wheel arches 

Most of the areas most prone to rust are underneath the car, but the wheel arches are subject to the most road dirt and grime than anywhere else. Wheel arches are often made up of an outer skin, and an inner structural panel.  

Why do wheel arches rust? 

As we mentioned above, the wheel arches catch any dirt, water, and road salt thrown up by the wheels. Rust will appear even faster if the area has a coating of mud, as this holds moisture against the steel.  

We also mentioned the way wheel arches are made; this sandwich of metal sheets is the perfect place for any moisture to pool; wheel arches often rust from the inside out. 

How much does wheel arch rust cost to repair? 

Because the rear wheel arch is an integral part of a car’s bodyshell, they can cost anywhere from £300 - £2,000 per side to have fixed. Front-wheel arches can usually be fixed by replacing the entire wing panel, budget around £500 for a rust repair.

This high cost is mostly due to the location, as the wheel arch is part of the main body of the car it cannot be unbolted and replaced, specialist welding, bodywork, and painting are required to create a repair that is as good as new. 

Sills 

Another common place for cars to show rust is on the sills, this is the section of the floor between the front and rear wheels that makes up the bottom section of the door frame. The sills, in conjunction with the door pillars and roof, make up most of the structure of a car. 

Why do sills rust out? 

In a similar fashion to the wheel arches, sills get barraged by all the road grime and water from the wheels, but that is only part of the story. Cars have drainage channels that route any rainwater to the floor, these run through the gaps between the doors, and then through the sills.  

When the drainage holes in the sills become blocked, often from built-up road dirt and leaves, the water sits inside the sill, causing it to rust out from the inside. 

How much does sill rust repair cost? 

Because the sills are a structural component, they need to be repaired properly to pass an MOT. Allow anywhere between £400 - £1,500 for a sill rust repair.

On most cars, the sill consists of two panels, the inner sill and the outer sill. If the rust is bad on the outer sill, it is likely the inner one will need to be cut out and a new panel welded in too. 

Boot floor 

A theme that you may be noticing, is that trapped water causes most of the rust issues on cars, the boot floor is no different. In particular, it’s often the spare wheel well that corrodes.  

Rust in the boot is an easy and important check to do when buying a used car. 

What causes rust in the boot floor? 

As mentioned, standing or trapped water is usually the cause of severe car rust. Any leaks in the boot seals will allow water in, which will eventually find its way to the lowest point. 

What is the cost of repairing boot floor rust? 

As the boot floor is not seen, rust repairs can be done at a more reasonable price, still allowing between £250 - £800, depending on the level of rust and the car.

Exhausts 

A difficult one to check, but exhaust rusting out is a common cause of MOT failure in older cars, it's also something that should be remedied as quickly as possible, as a rusty exhaust could well be causing fumes to leak into the cabin. 

What causes exhausts to rust? 

Rusting exhausts are not an uncommon ailment on older cars, often causing the exhaust to leak, and eventually fall off the car.  

There are two main causes of exhaust rust;  

• Road salt/water 
• Condensation.  

The former cannot realistically be avoided, as the exhaust is routed directly under the car, and is in the firing line for any puddles and debris the wheels drive through. Condensation on your exhaust, however, can be avoided by reducing short journeys. 

When your car is parked up, water will condense inside the cold exhaust pipe, a long journey will give the hot exhaust gases enough time to fully vaporise this into steam. Shorter journeys might not, causing a build-up of water inside the exhaust pipe which can, over time, cause rust. 

How much does it cost to fix a rusty exhaust pipe? 

As most exhaust pipes are made of plain steel (and not stainless steel) they will typically cost between £175 - £500 to replace. 

Thankfully, exhausts are bolted to the engine, with rubber mounts holding them to the body. This means they are generally very easy for a garage to replace.

Suspension Components 

Suspension arms, springs and shock absorbers are also subject to road water, dirt, and salt. Older or high-mileage cars therefore can experience higher levels of rust in these areas.  

What causes the suspension to rust? 

Whilst most wishbones, control arms and springs are painted, to protect from rust, suspension components are prone to receiving impact from stones and other debris during normal usage.  

This damage to the paint, combined with constantly being soaked with water and salt, results in a part that's susceptible to rust, more than most. 

How much does suspension rust cost to fix? 

Like exhausts, suspension components can be unbolted and cheaply replaced. £125 - £500 would be a reasonable price to pay for new suspension arms and springs on a standard family car.  

Is rust on my car dangerous? 

Depending on the location and severity, rust could seriously affect the safety of your vehicle. Areas that need the most attention are suspension components, sills and subframes. 

Very minor bodywork rust, in places such as the wheel arches, roof, boot lid, doors and front wings, should not present immediate danger, but do not allow it to become severe enough to cause sharp edges, or to the point where structural integrity is compromised. 

As rust is an ongoing problem, we’d suggest getting it sorted as soon as possible to reduce the likely cost of fixing. 

Will my car fail the MOT for rust? 

If the rust is considerable, and on a structural component, such as the sill, suspension components or subframe it will fail an MOT. Similarly, rust on the bodywork within a specified distance of suspension mountings or seat belt anchorage points will also not pass an MOT. 

Can I fix rust myself? 

If your car has signs of rust, it may be possible to touch up certain areas at home. This is only really possible on purely cosmetic patches, that are only on the surface of the panel. Any areas that have rusted from the inside out, or that are on structural components, will need a skilled welder to fix.  

Products such as rust converter paints are available, that generally require the surface to be cleaned of excess paint and corrosion, before being painted on liberally. These paints “convert” the rusted metal into a solid material, and inhibit future rusting.  

The area would then need to be painted with the correct, colour-matched paint and top coat.  

How to prevent rust on your car 

Rust is one of those issues that needs constant preventative maintenance, best done well before the car has started rusting at all.  

Undersealing is a paint that covers the underside of the car, to reduce the amount of water that can touch bare steel, preventing rust. A similar product can be injected into sills and wheel arches. 

Ask an expert 

So there you have it, rust can present a big problem for car owners if the issue isn’t fixed. If you’re unsure about how bad your rust problem is ask one of our experts. 

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