The Defender 110 is especially prone to underbody corrosion and the proof can be seen in as little as 2-3 years depending on the climate. Newer model vehicles are more effectively rust proofed at the factory, but even those could benefit from protective undercoating from time to time. Defenders driven in high-salt areas, off-road and in mud, or submerged in water need to be undercoated more frequently.

There are four main methods to help undercoat the underbody of your Defender to prevent underbody corrosion: 1- rust killing paint spray, 2- rubberized undercoating spray, 3- tar-based undercoating best applied with brush, and 4- wax and oil-based undercoating spray.

Maintaining a rust-free underbody prolongs the life of your chassis, brake lines, engine, gearbox and transfer case parts, suspension system, underbody hardware, and almost all the components under the vehicle.

Shown above, the underbody is sanded and painted with Rustolium flat black undercoat paint. Using a flat head screw driver and 400 grit sand paper, rusted surfaces are scraped and sanded to a smooth finish. Body is sprayed one thin coat of paint at a time. Ten minutes later a second coat is applied. You will find many underbody crevices and components which are difficult to reach. Use a combination of hand tools to reach these hard to reach areas. Any rust left behind will contaminate the area next to it and result in damaging the rusted area further without early detection.

It works better to undercoat a vehicle once the vehicle is fully lifted using a hydraulic jack. If you do not have access to a hydraulic jack and must apply undercaot by leaning on the floor under the body, make sure to wear a mask and goggles, and leave plenty of room for ventilation. The result of a good underbody Rustolium spray job can last anywhere from a couple of years to a few depending on the quality of prep work as well as the frequency of exposure to a corrosive environment.

The easiest and least costly method of undercaoting the Defender is spraying it with rust-eating paint. Rustolium and similar products can kill rust in a matter of hours and provide good adhesion to sanded and cleaned metal surfaces. This type of undercoating needs to be inspected for flakes from time to time. Once the paint starts flaking off in any area, that area needs to be sanded and cleaned, and one or two new coats of rust-killer paint needs to be applied. Shown above, two or three thin coats of paint applied in 25 minute intervals will last longer than one heavy coat applied at once. Other options include rubberized or tar-based coatings. While both provide a thicker and somewhat more robust undercoat protection to the underbody, both are prone to cracking and chipping, allowing water to settle between the coating and underbody surface.

Inspect trapped water pockets under the coating by scraping away the coating around questionable areas. Detecting trapped water in this case is more difficult visually than detecting Rustolium failed undercoat paint.

An alternative method is the use of WaxOil®, a product made of two main components, melted hard wax and protective oil. Using rust removal tools, once surface rust has been removed and the surface cleaned, the wax and oil are thinned out and sprayed throughout the underbody, into door access panels and hard to reach areas using a specialized spray nozzle. This coating does not allow water to trap under it and does not flake off like paint or rubberized undercoating. Instead, it can be smeared off when rubbed against a solid surface. The final product gives a somewhat oily and waxy finish to the underbody, considered messy by some users. However, WaxOil provides the most substantial solution to protecting the underbody of your Defender against rust and corrosion. The compound comes in square cans or in ready to spray cans. It is the costliest of all four solutions.