How to Repair Car Rust
FixMyCar discusses how rust can affect your vehicle and how to treat it.
Book a car repair nowEllie Dyer-Brown
Wednesday January 15 2025
9 min read
Rust can be a real problem, not just for cosmetic reasons. It's a known silent killer. The longer you leave it, the worse it gets until the vehicle's structure is no longer safe.
The best solution is to find a bodyshop specialist who can restore your car to a professional standard. However, it's possible to fix minor cases of rust at home. In this guide, find out everything you need to know about rust and how to remove it.
What is rust?
Rust is created when iron reacts with oxygen and water, resulting in an unsightly orange stain that begins to corrode the metal; this is known as iron oxide. Many different things can cause cars to rust, and some speed up the process considerably.
Age is one of the most significant factors. As the years go by, the paintwork is subjected to wear and tear, eventually exposing the bodywork underneath. When this happens, the metal is vulnerable to rust because it directly interacts with moisture and air.
Climate can also affect the speed at which your vehicle rusts. Living near the sea, for example, can make cars rust faster than usual because there is salt in the air. Even the type of salt that’s used on roads can cause corrosion.
Types of rust
There are three types of rust, some being more severe than others.
Penetrating rust is, as you might expect, the most damaging kind. If left untreated, it will eventually cause the corrosion of entire panels and parts that must be replaced.
Scale rust happens when surface rust is left too long and begins corroding the metal.
Surface rust is the least damaging and most straightforward to treat. It only affects the top layer of your car and usually happens in places that have been bumped or scratched.
How to repair car rust
Minor rust damage can be repaired at home if you’re willing to invest in the right tools, but it’s a process that must be done carefully and precisely to get high quality results.
Tools & materials
Fibreglass epoxy gel
Wire brush
Angle grinder and flapper wheels
Assorted grades of sandpaper
Body filler
Sanding block
Primer and base coat paint
2k clear coat paint
Masking materials (tape and paper)
Mineral spirits
Rubbing compound
Rags
Tack cloth
Instructions
1. Remove rust
Use the angle grinder and flapper to remove rust and paint from the affected area. Alternatively, you could do this by hand using coarse 80-grit sandpaper and a wire brush, but it’s much harder to be thorough this way.
If you can’t reach the area with an angle grinder, use the wire brush to remove as much dirt and rust as possible. A rust converter, which chemically neutralises rust and leaves a protective black coating, can help.
2. Repair with fibreglass
Using long-strand fibre repair gel allows you to create a structural repair that is nearly as strong as steel. Mix the gel and hardener and press it into the affected area from behind. It usually starts to harden in about 15 minutes and can be sanded in less than an hour, but you should check on the back of the packet to make sure.
3. Sand excess fibreglass
Sand off any excess glass fibre gel using the angle grinder and flapper. The surfaces of the rust holes should be slightly indented compared to the metal panel so it can be filled with body filler, which gives a much smoother finish.
4. Apply body filler
Mix the body filler with the correct amount of hardener. Press the filler into the rust holes using a flexible, flat spreader. The flatter you can get during application, the less sanding you’ll have to do later. Make sure you apply enough filler to avoid low spots, pinholes or scratches - you don’t want to have to apply a second coat.
5. Sand it until smooth
Getting a smooth surface on bodywork repairs is crucial. It can be time-consuming, but it will make the outcome look professional. Begin with 400 or coarser sandpaper and sand off excess filler - this process is faster if the filler hasn’t gone completely hard. If you have a large area to sand, you may need a sanding block to ensure you end up with a flat surface. This step is finished when the area is entirely smooth to the touch.
6. Clean area
Wipe the sanded area with a clean rag and mineral spirits. The body filler should be thin enough to see metal and paint through it in most places. Wash the area with a tack cloth to remove lint when dry. Cleanliness is crucial to ensure a consistent paint job.
7. Prime the area
Spray a thin coat of primer over the repaired area and about an inch around it for blending. Go over the first coat again a few minutes later with a slightly heavier coat and let it dry completely before sanding.
8. Wet-sand and repeat
Use 400 grit sandpaper to wet-sand the primed area until smooth, and the edges are feathered into the original paintwork. Give it a wipe to clean it, allow it to dry, and spray another coat of primer. Now, switch to 600-grade sandpaper and repeat the wet-sanding process. Two or three coats of primer should be enough.
9. Spray the base coat
Modern cars typically use a base coat of colour covered with a thicker clear top coat, although many touch-up paints can be used alone. Spray two or three thin coats of paint over the primer and into the original paint. It’s best to use several thin coats rather than one thick coat.
10. Rub out the paint
To achieve a glossy finish from spray can touch-up paint, you need to run it by hand with a polishing compound. If there are any significant mistakes from the paint job, you’ll need to start with wet-sanding using 1,000 and then 2,000 grit. Avoid going too far, or you’ll have to apply another coat of paint.
When ready, polish the paint job lightly with rubbing compound before moving up to a finer polishing compound to achieve a shiny gloss.
11. Spray the clear coat (optional step)
Applying a clear coat is the optional final step. If you plan on keeping the car for a long time, we’d recommend doing this using 2K clear paint, which will make the repair much longer lasting and almost as durable as a professional body shop paint job.
What does rust look like?
We all know that rust is usually brown or orange, but there are other symptoms to look out for.
Bubbles in the paintwork should be an immediate cause of concern; they indicate that air has got in between the paint and metal, so it won’t be long until rust starts forming. Any scratches or dents, particularly where the paint has been damaged, will likely develop rust.
Finally, if you notice any puddles on the carpet inside your car - particularly in the boot or footwells - this could be a sign that the metal beneath has rusted.
Where does rust usually happen?
Rust is easiest to spot when it’s on the outside of the vehicle, but you’d be mistaken in thinking that just because a car appears to be free from rust, it actually is. Sometimes, rust begins inside a panel and spreads outward.
If you’re worried about rust, always check your exhaust, suspension, wheel wells and frame rails, as these are most susceptible.
Can you paint over car rust?
The answer, unfortunately, is that it depends. Light rust on the vehicle's surface might be repaired with a paint job, but only if the correct procedure is followed; it isn’t as simple as painting over the top of the rust to disguise it.
Average cost to repair rust bubbles
The cost of repairing rust bubbles depends on the extent of the problem; if they only cover a small area, this is an easy job for a body repair shop and should be relatively inexpensive.
However, the cost will be much higher if rust bubbles appear all over your vehicle. The best way to find out how much it will cost is to post a job on FixMyCar. Reliable garages in your area will get back to you with quotes, allowing you to find the best price.
How to prevent rust damage
Maintaining your vehicle is an essential part of rust-proofing. Here are a few steps you can take to protect it from rust spots:
1. Keep your car as dry as possible.
Of course, this can be a challenge thanks to the sheer amount of rain we see here in the UK, but something as simple as parking your car in a garage rather than on the street when you're not using it can have a positive impact.
2. Wash and dry.
This is particularly important if you live near or travel to the seaside regularly. When you get home, quickly wash down your vehicle with the hose pipe and dry it off with a chamois. This helps to prevent salty air from damaging parts of the car.
3. Use oil and wax.
Wax adds an extra layer of protection to your car's body panels, and applying a squirt of WD40 will help to remove water from areas that are most susceptible to damage (and are usually hard to reach).
Best rust treatment for cars UK
Rust converters are chemical solutions that chemically convert iron oxide (rust) into a more stable compound, leaving a hard shell behind that can be painted or sprayed with a protective compound.
Below are three of the best rust treatments.
Jenolite Rust Buster Spray
Around £18 for 400ml
Spray application
Economical
Distributes evenly
Tricky to apply to some areas
Rustbuster Fe-123
Around £21 for 500ml
Brush application
Thick formula prevents drips on vertical surfaces
Ready to paint after 30 minutes
Available on Rust.co.uk.
Bilt-Hamber Hydrate-80
Around £20 for 500ml
Brush application
Soaks into rust quickly
Decent value
Not as effective as other options
Rather have someone else repair the rust for you? FixMyCar can help you find a car body repair shop to do it quickly and professionally, returning your vehicle to its original glory.
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Ellie is FixMyCar's Content Manager. She has over three years of experience writing about cars and regularly collaborates with automotive experts to provide trustworthy advice for drivers that is easy understand. Her work has been featured in Yahoo! Finance, iNews, The Daily Express and The Sun. She has a BA in English literature and an MA in creative writing from Durham University. Outside of work, Ellie follows F1 and eagerly awaits Ferrari's next era of dominance in the sport. She drives a Suzuki Swift.