Professional Underbody Rust Prevention and Chassis Protection

Thoroughly wash the undercarriage using a high-pressure cleaner. Focus on 'mud traps' such as the tops of fuel tanks, inside chassis rails, and behind wheel arch liners. Use a salt-neutralising wash mixed at a 1:100 ratio if the vehicle has been on a beach recently. All dirt must be removed, as any trapped debris will hold moisture under your new coating.

Inspect the chassis for existing rust. Use a wire brush or a drill-mounted wire wheel to remove loose flakey rust (scale) until you reach solid metal. You do not need to remove all staining, but the surface must be structurally sound. In Australia's heat, loose rust can act as a sponge, so this step is critical for long-term adhesion.

Apply a heavy-duty alkaline degreaser to all metal surfaces to remove oil leaks and road film. Rinse thoroughly. The vehicle MUST be completely dry before applying oil-based or wax-based inhibitors. In summer, 2-3 hours in the sun is usually sufficient, but use compressed air to blow out water trapped in boxed sections.

Identify 'no-go' zones. Use painters tape and plastic bags to cover the exhaust system (especially the catalytic converter/DPF), brake rotors, brake calipers, and rubber bushings. While lanolin is rubber-safe, bitumen-based products can cause rubber to swell and perish. Covering the exhaust prevents foul smells and smoke when the vehicle reaches operating temperature.

Insert the 600mm extension wand of your cavity wax (e.g., Tectyl) into every available hole in the chassis rail. Depress the nozzle while slowly withdrawing the wand at a rate of roughly 10cm per second. This ensures 360-degree coverage inside the boxed sections where condensation sits and rust starts unseen.

Repeat the cavity injection for cross-members, door pillars (if accessible), and the inside of the 'A' and 'B' pillars. These areas are notorious for trapping red dust which, when combined with coastal humidity, causes rapid internal perforation.

Set your spray gun or aerosol to a wide fan pattern. Begin at the front of the vehicle and work backwards. Apply a liberal coat of heavy-duty lanolin or chassis shield to all exposed metal. Aim for a 'wet' look without excessive dripping. Lanolin is ideal for summer as it remains 'active' and flows into cracks as the metal expands.

Apply a second, thicker layer to high-impact areas: the front of the differential, the leading edge of the suspension arms, and the inner wheel arches. These areas are sandblasted by road debris and require a thicker sacrificial layer to maintain protection.

Lightly coat the leaf springs or coil seats. For leaf springs, the lubricant properties of lanolin can actually reduce 'squeak' and friction between the leaves, though avoid getting excessive amounts on the spring dampers (shocks).

Spray a light mist of non-conductive lanolin or specialized contact protector over the exterior of electrical plugs and grounding points. This prevents the 'green death' (copper oxidation) common in vehicles exposed to salt air and high humidity.

Using a high-lumen torch, inspect the underbody for any 'shadows' or uncoated spots. The red dust of the outback will find any unprotected metal within kilometers. Ensure the top side of the chassis rails—visible through the wheel arches—is fully coated.

Carefully remove all plastic bags and tape from the exhaust and brakes. If any overspray has reached the brake rotors, clean them immediately with a dedicated Brake Cleaner solvent and a lint-free rag. Contaminated brakes are a severe safety risk.

Allow the coating to 'set' for at least 4-6 hours before driving. In temperature extremes over 35°C, the coating may appear slightly tacky; this is normal for lanolin-based products and indicates the product is migrating into the metal pores.

A professional secret: After the coating has cured for 24 hours, drive the vehicle on a dry, dusty (not muddy) road. The fine dust sticks to the protective coating, creating a 'crust' that adds an extra layer of physical protection against stone chips. This is particularly effective for lanolin treatments.