Best rust converters 2026
We find the best product to stop your car slowly corroding into dust
If you think modern motors are immune to rust, take a look at the underside of cars that have been driven through a few winters. You’ll see corrosion on suspension arms, brackets and fasteners. Leave it a little longer and the MoT tester might start to poke holes – sometimes literally – in your chances of getting a clean pass, especially if you live in areas near the sea or where winter road gritting is more frequent.
To stop the rot you will need to get busy with a wire brush and some rust converter. These potions contain chemicals that react with the rust and turn it into a coating that can be painted or wax-protected to give your car the best chance of survival. We tested seven rust busters to see which one is the best.
How we tested
To simulate rusting car bodywork, we left samples of 1mm thick mild steel outside until they had developed a uniform level of corrosion. Both sides of the sheets were then treated with the rust converter fluids. Once dry, we painted one side with aerosol primer followed by a metallic top coat. The samples were left outside for four months and sprayed on both sides with salty water daily.
Nitromors Rust Converter
- Price: around £17.99
- Size: 500ml
- Cost per 100ml: £3.60
- Rating: 4.5 stars
- Contact: nitromors.com
Used - available now
2021 Mercedes
A-Class
79,566 milesAutomaticDiesel2.0L
Cash £12,790
2022 MINI
Countryman
14,343 milesAutomaticPetrol1.5L
Cash £21,840
2019 Hyundai
Ioniq hybrid
73,006 milesAutomaticPetrol1.6L
Cash £10,649
2017 Renault
Captur
60,494 milesManualPetrol0.9L
Cash £5,990Our new, tougher testing regime suited the Nitromors, but with a proviso. While the painted side showed the least corrosion of any of the samples in this test, the surface that had been
left with just the Nitromors treatment alone was showing some clear signs of rust. That means this product is at its best only when you use it as a base for other coatings. Bear that in mind and it is easy to use and apply, with a thin liquid which soaks into the surface quickly. It’s decent value, too.
Jenolite Rust Converter Spray
- Price: around £19.99
- Size: 500ml
- Cost per 100ml: £4.00
- Rating: 4.0 stars
- Contact: jenolite.com
Unlike the rivals here, the Jenolite is applied by aerosol rather than being painted on. The resulting spray is waxy, which means it sticks on vertical surfaces without dripping. This could make it ideal for spraying onto inaccessible areas under a car, such as behind the wheelarch liners.
That waxiness also meant the unpainted side fared well at the end of our test, with large patches that remained coated and rust free. The paint didn’t seem to stick quite as well to the other side though, and this looked scruffier than the Nitromors-covered item.
Bilt Hamber Hydrate 80
- Price: around £19.95
- Size: 500ml
- Cost per 100ml: £3.99
- Rating: 4.0 stars
- Contact: bilthamber.com
The milky Hydrate 80 is easy to apply because it soaks quickly into the rusty surface of the steel, even on vertical surfaces, and quickly reacts to turn the corrosion black.
At the end of the test period, the side that had been left unpainted still looked well protected, with areas of the black coating still clearly visible.
The painted side didn’t fare so well, with patches of corrosion showing. Although it’s not the most expensive, a recent price rise has knocked some value points off the Hydrate’s overall score.
Rustbuster FE-123
- Price: around £18.50
- Size: 500ml
- Cost per 100ml: £3.70
- Rating: 3.5 stars
- Contact: rust.co.uk
Rustbuster’s FE-123 has a thicker, creamy consistency that makes it easier to apply to vertical surfaces. It also takes around half an hour to react with the metal, which sounds like a disadvantage but actually makes it easier to see where you have treated. After two hours it is tough enough to paint. The FE-123 had clearly given some protection to both sides of our steel sample, but the rust was returning around the edges.
Rustins Rust Converter
- Price: around £11.49
- Size: 250ml
- Cost per 100ml: £4.60
- Rating: 3.0 stars
- Contact: toolstation.co.uk
The smaller bottle of Rustins might suit someone who has only a tiny amount of rust to tackle, such as a few stone chips. But it does hit the value score, because converters with double the volume cost only a few quid more.
This might be forgivable if it was more effective, but the Rustins didn’t offer any more protection than its rivals here. Some of the glossy coating was visible at the end of our test, but in most other parts the rust had bitten into the metal.
Hammerite Kurust
- Price: around £13.00
- Size: 250ml
- Cost per 100ml: £5.20
- Rating: 2.5 stars
- Contact: halfords.com
If you are in a hurry, the Hammerite was the converter that seemed to work fastest, with the liquid acting instantly to turn the rusty metal black. This, plus the high price and Hammerite’s reputation for corrosion-killing products, made us hopeful that it would be effective in protecting our metal sample.
Sadly, the sample was uniformly rusty on the bare side and looked seriously scruffy on the painted face as well.
HIKQ 2-in-1 Rust Reform & Seal
- Price: around £2.58
- Size: 50ml
- Cost per 100ml: £5.16
- Rating: 1.0 stars
- Contact: temu.com
Temu sells some excellent car accessories, but this isn’t one of them. The tiny 50ml bottle has a spray nozzle to dispense a liquid that’s claimed to reform and seal rust. But it seemed to have no effect other than wetting the metal.
By the end of the test the sample was clearly the most corroded. Its £2.58 cost does include a useful brush though, which is what earns this product its single star.
Verdict
The Nitromors Rust Converter came out top, but it is at its best when painted over after application. If that’s not practical for you, then the Jenolite Rust Converter Spray offers a good alternative. Third goes to the Bilt-Hamber Hydrate 80, which protected the unpainted metal and is easy to apply.
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