Comprehensive Underbody Rust Prevention and Corrosion Control

Thoroughly inspect the entire chassis using a high-lumen torch. Use a small hammer to lightly tap along the chassis rails; a 'sharp' ring indicates healthy metal, while a 'thud' suggests internal rust or packed mud. Mark areas of concern with a paint pen for focused treatment later.

Raise the vehicle on a level concrete surface using a high-lift jack and secure it on heavy-duty jack stands at the factory lifting points. Removing the wheels provides critical access to the wheel arches, brake lines, and suspension components that are often missed.

Place large heavy-duty tarps or drop cloths beneath the vehicle. Underbody cleaning releases significant amounts of grease, salt, and red dust. In summer, ensure you are working in a shaded, well-ventilated area to prevent cleaning chemicals from drying prematurely on the surface.

Mix your salt neutraliser and degreaser according to the manufacturer's instructions for 'heavy soil'. Typically, a 1:10 ratio for degreaser and 1:500 for salt neutraliser is standard. Ensure your pressure washer is connected to a stable water source and the underbody wand is fitted.

Begin with a high-volume, low-pressure rinse to soften and remove bulk mud and red dust. Focus on the 'mud traps' behind the wheel arches, on top of the fuel tank, and inside the bumper bars. Continue until the runoff water transitions from brown/red to clear.

Apply the heavy-duty degreaser to the entire undercarriage. Let it dwell for 8-10 minutes, but do not allow it to dry (mist with water if working in 30°C+ heat). Use a long-handled brush to agitate areas with heavy grease buildup, particularly around the transmission and differentials.

Apply the salt neutralising solution using a foam cannon or low-pressure sprayer. This chemical step is vital as salt is hygroscopic (attracts water). The neutraliser breaks the chemical bond that normal water cannot. Let it sit for 5 minutes before a thorough high-pressure rinse.

Identify any areas with existing surface rust. Use a wire brush or a drill-mounted wire wheel to strip the rust back to bright metal. This ensures the protective coating adheres to the substrate rather than just covering a pocket of active oxidation.

Insert the pressure washer's drain cleaning hose or chassis wand into the factory drainage holes. Flush the inside of the rails until the water exiting the rear drainage points is completely clear of silt and debris. This is where most 4x4s rot from the inside out.

Immediately dry the chassis using compressed air, focusing on seams, bolt heads, and crevices. In the Australian summer, evaporation is fast, but trapped water in boxed sections is the enemy. Use a leaf blower for 15 minutes to ensure maximum airflow through the chassis rails.

Use masking tape and plastic bags to cover the brake rotors, exhaust system (especially the catalytic converter/DPF), and any rubber bushings or boots if using a solvent-based coating. Lanolin is generally rubber-safe, but keeping it off brakes is a safety priority.

Using the 360-degree extension wand, spray cavity wax deep into the chassis rails, door bottoms, and sills. Pull the wand out slowly (approx. 10cm per second) to ensure an even, thick coating. This wax displaces any remaining moisture and seals the internal metal.

Apply your chosen underbody sealant (Lanolin) starting from the front of the vehicle and moving backward. Keep the spray gun 15-20cm from the surface. Ensure a 'wet' look is achieved. Lanolin is excellent for Australia as it doesn't dry hard; it remains 'active' and will creep into new stone chips.

Apply a second coat to high-impact zones: the leading edges of the suspension arms, the inner wheel arches, and the rear of the chassis where the tyres throw up sand and stones. These areas experience the most 'sandblasting' during off-road driving.

Allow the coating to 'set' for at least 2 hours before moving the vehicle. Use a torch to check for 'holidays' (missed spots). The coating should look uniform. If using lanolin, it will remain slightly tacky, which is normal and part of its protective function.

Remove masking from brakes and exhaust. Reinstall wheels and torque lug nuts to factory specifications (usually 100-120Nm for most passenger vehicles/SUVs). Wipe down any overspray on the exterior paint using a microfiber cloth and a mild solvent or IPA.