Comprehensive Underbody Rust Prevention and Chassis Protection

Begin by thoroughly pressure washing the entire undercarriage. Focus on 'mud traps' such as the tops of fuel tanks, inside wheel arches, and behind bumpers. Use a salt-neutralising wash mixed at a 1:500 ratio if you have recently been to the coast. This removes the hydroscopic salts that pull moisture into the metal even in dry weather.

Inspect the chassis for existing rust. Use a wire brush or a needle scaler to remove loose flakes. The goal isn't to reach shiny metal, but to remove anything that might peel off later. If you leave loose scale, your protective coating will simply fall off with the rust flake, leaving the metal underneath vulnerable.

Apply a heavy-duty degreaser to the engine bay (lower sections), gearbox, and differentials. Oil leaks will prevent rust inhibitors from bonding correctly. Allow the degreaser to dwell for 10-15 minutes—ensuring it does not dry in the heat—before rinsing thoroughly with hot water if available.

The chassis must be bone dry before applying oil or wax-based inhibitors. In 40°C summer heat, 2 hours in the sun is usually sufficient. Use compressed air to blow out water trapped in 'U' channels and boxed sections. Any trapped water will be sealed in by the protectant, potentially causing 'inside-out' corrosion.

Use masking tape and plastic sheeting to cover brake rotors, calipers, the exhaust manifold, and the drive belts. You do not want slippery rust inhibitors on braking surfaces or causing belts to slip. Cover the exhaust system from the catalytic converter back to prevent the smell of burning oil during the first few drives.

Insert the 360-degree extension wand into every available hole in the chassis rail. Slowly withdraw the wand while spraying to ensure an even internal coating. These areas are the most common failure points because they collect red dust which holds moisture against the inner walls of the steel.

Set your spray gun to a wide fan pattern and 40-50 PSI. Begin at the front of the vehicle and work backwards. Apply a thick, even coat of lanolin-based sealant to all exposed steel. The coating should look 'wet' but not be dripping excessively. Aim for a thickness of approximately 200-300 microns.

Apply a second 'cross-hatch' coat to high-impact zones like the front of the differential, the leading edges of control arms, and the inner wheel arches. These areas are constantly sandblasted by road debris and require a thicker sacrificial layer to maintain protection.

Lightly mist lanolin over exposed electrical plugs and grounding points. Lanolin is non-conductive and hydrophobic, meaning it will prevent 'green crusties' (copper oxidation) in wiring looms, which is a common cause of electrical gremlins in coastal vehicles.

If your vehicle has leaf springs, spray the inhibitor between the leaves while the suspension is slightly unloaded (vehicle on stands). This lubricates the leaves, reducing 'squeak' and preventing rust from binding the pack together. Avoid heavy saturation of rubber bushings as some oil-based products can cause swelling.

Use a high-lumen torch to inspect the coating. Look for 'holidays' (missed spots) which appear dull compared to the glossy protected areas. Pay close attention to the top of the chassis rails near the tub or tray, as these are often missed but highly susceptible to salt air.

Before the product sets, use a microfibre cloth dampened with a mild solvent to wipe away any overspray on the exterior paintwork. Lanolin is safe for paint but will attract dust immediately, making it difficult to remove once it thickens in the sun.

Allow the vehicle to sit in a dust-free environment for at least 4 hours. In summer temperatures, the carrier solvents will evaporate quickly, leaving behind the protective wax or grease. Do not drive on dirt roads for at least 24 hours to prevent dust from embedding too deeply into the fresh coating.

Once finished, ensure all drain holes in the chassis and doors are clear. Sometimes the thick protectant can clog these holes. Use a small zip-tie or wire to poke through and ensure water can still escape. A blocked drain hole is a guaranteed recipe for future rust.