Rustproofing – a stitch in time…

Posted on August 10th, 2021 by Rob Marshall

Rustproofing - a stitch in time...


Cars do not rust like they used to, so many people claim. In the main, they are right; rust holes are not common on five-year-old vehicles any more. Improved metal, galvanising, sealing and painting have improved matters immeasurably but rust has not been stopped in its tracks entirely, especially as many car manufacturers do not underseal beneath their vehicles.


Hidden from view

Modern cars also hide rust very well. You may not see ugly brown marks breaking out through otherwise glossy paintwork, but we see surprisingly young vehicles with corrosion breaking out on their undersides. The worse affected areas tend to be the around the boot floor sections, a location that is vulnerable to water and dirt being flung up by the tyres.


Regular maintenance needs

Naturally, mud accumulations hold moisture against the metal and this encourages rust spread, especially when saturated with wintertime road salt. Rinsing the underbody regularly is a good idea to release these build-ups, revealing any blistering paint and/or underlying corrosion.


Inspection and cure

Rust is not easy to remove and the car will need raising on ramps to access the underside. Within a home environment, this means raising the car an axle at a time, typically by driving it onto a pair of ramps and crawling underneath with a torch. Never venture beneath a car supported by a jack.

The rust removal process is relatively complex and depends on the extent of the corrosion. You need to remove as much brown iron oxide as possible, treat the remaining rust with a chemical converter, and complete the process by applying underseal. Always follow the product instructions.


Regardless of your approach, rustproofing is a messy task and should be performed when the car is dry. Therefore, summertime presents an ideal opportunity to conduct the work from home – just wear overalls, or old clothes, and protect the floor.


Rob Marshall is GEM’s technical adviser and is a freelance automotive and technical journalist.