Rail Dust

Rail dust is iron particles which statically become attracted to your car. 

They get the name 'rail dust', because it is common to see on vehicles which are parked by railway lines, however metal particles can come from a wide range of sources including your own car's brakes. It can be contained in soot from factory exhaust or caused by grinding and welding, and for this reason is falls under the classification of "industrial fallout".

Once iron particles stick to your car, they react with moisture in the air and rust, and this can eat into the paintwork and cause permanent damage. 

Depending on the severity of the contamination, rail dust can be removed in a number of ways, either by using clay bar or clay pads, or by using a chemical treatment which dissolves the particles without damaging your paintwork.

What it means

Rail dust is a type of bonded contamination made up of tiny iron particles that stick into the clearcoat of your car. They often come from train wheels and brakes, lorry and car brakes, nearby industry and even the transporters that move new cars by rail. Once embedded, the particles start to oxidise (rust), showing up as tiny orange or brown specks, especially noticeable on white and silver paint. Because the particles are physically lodged in the clearcoat, normal washing and shampoo will not remove them.

Why it matters

• Looks like rust spots: The little orange specks can make otherwise clean paint look dirty, peppered and neglected, particularly on light colours.
• Can stain the clearcoat: If left for a long time, the rusting iron can stain deeper into the clearcoat, making complete removal harder and sometimes leaving shadows.
• Interferes with polishing and coatings: Embedded metal particles act like grit under a polishing pad and can reduce the bond and durability of waxes, sealants and ceramic coatings if not removed first.
• Indicator of environment and storage: Heavy rail dust often shows a car has spent time near railways, freight yards or industry, which can be relevant when assessing used cars and lease returns.

Where you’ll see it

You will see the term “rail dust” on detailing inspection sheets, decontamination service menus and technical articles about iron fallout removal. It is commonly mentioned when explaining why a “new” car still needs decontamination, why white cars pick up orange dots, or why an iron fallout remover (the product that bleeds purple) is being used.

Context

Rail dust is part of the wider category of industrial fallout and bonded contamination. Detailers typically tackle it with iron fallout removers that chemically dissolve the iron particles, followed by clay bars or clay pads to remove anything left behind. Proper removal is an important step before machine polishing or applying long-term protection. Although the name suggests it only comes from trains, in practice many of the particles also come from road traffic and nearby industry, so you can find rail dust even if you live nowhere near a railway line.

Common mistakes

• Assuming the orange spots are rust coming through from the metal panels, when they are usually rusting particles sitting in the clearcoat.
• Trying to scrub rail dust off with harsh sponges or brushes and adding extra wash marks and scratches to the paint.
• Skipping iron fallout remover and claying, then machine polishing over embedded rail dust and dragging metal particles around the panel.
• Applying wax, sealant or ceramic coating straight over heavy rail dust contamination, which traps the particles in place and reduces the performance of the protection.

Written by Danny Argent. Last updated 18/11/2025 17:44