Comprehensive Boat Trailer Maintenance and Corrosion Protection Guide

Before applying water, inspect the trailer for 'white rust' (zinc hydroxide) and 'red rust' (iron oxide). Use a high-lumen torch to look inside box sections and under the mudguards. Check for cracks in the galvanising, particularly around the leaf spring hangers and the winch post, which are high-stress areas.

Connect the trailer to the vehicle and test all lights. In our heat, plastic lens covers can become brittle and crack, allowing salt air to corrode the bulb sockets. Check the 7-pin or 12-pin plug for green copper-sulphate corrosion; if present, it must be cleaned with contact cleaner before proceeding.

Position the trailer on a hard, flat surface with adequate drainage. Ensure you are not working over sensitive lawn, as salt-neutralising chemicals and degreasers can alter soil pH. If working in summer heat, try to find a shaded area or work in the early morning to prevent chemicals from drying too quickly on the metal.

Mix your salt neutraliser according to the manufacturer's ratio (typically 1:500 for a venturi-style applicator or 100ml per 5L for manual spraying). Prepare a bucket of warm soapy water using a high-foaming automotive soap to help lift red dust and road film.

Using a salt-neutralising solution, flush the entire frame. Start from the front (hitch) and move toward the rear. Pay special attention to the inside of the box sections—insert the nozzle into the drain holes and flush until the water runs clear. This removes the salt crystals that cause internal 'hidden' rot.

Spray a heavy-duty degreaser onto the axle, leaf springs, and hubs. Let it dwell for 5-7 minutes, but do not allow it to dry. Use a stiff brush to agitate the grease and road grime buildup. This is critical for inspecting the integrity of the suspension components.

If red rust is present on the axle or springs, use a wire brush to remove loose flakes. For galvanised frame sections showing 'white rust', lightly abrade with a Scotch-Brite pad. You must reach solid metal or stable galvanising for any touch-up paint or barriers to adhere properly.

Apply a zinc-rich cold galvanising spray to any bare metal or areas where the original galvanising has worn thin. Apply two light coats with a 15-minute flash-off time between them. This provides sacrificial protection, where the zinc corrodes instead of the underlying steel.

Remove the dust caps or Bearing Buddies. Inspect the grease for a 'milky' appearance, which indicates water ingress. If the grease is clear, use a grease gun to pump fresh marine grease into the nipple until the spring compresses or fresh grease begins to exit. If milky, the bearings must be pulled, cleaned, and repacked.

For trailers with mechanical disc brakes, apply a small amount of marine grease to the slider pins. Ensure no grease touches the brake pads or rotor faces. For hydraulic systems, check the master cylinder fluid level and look for leaks around the calipers or wheel cylinders.

Check tyre pressures against the placard (usually 45-60 PSI for light truck trailer tyres). In our 40°C+ summers, under-inflated tyres build up immense heat, leading to delamination. Inspect sidewalls for UV-induced 'crazing' or cracking; if cracks are deeper than 1mm, replace the tyre regardless of tread depth.

Unwind the winch strap or cable fully. Inspect for fraying or UV damage. Lightly coat a steel cable with lanolin spray to prevent rust. Lubricate the winch gears with a heavy-duty grease to ensure smooth operation under the load of the boat.

Once the trailer is completely dry, spray a liberal coating of liquid lanolin over the entire axle, leaf springs, and the rear 1/3 of the trailer frame (the section most often submerged). Lanolin is a natural wool grease that does not wash off easily in saltwater and provides an airtight seal.

Leaf springs are the 'Achilles heel' of boat trailers. Ensure the lanolin or grease penetrates between the leaves. Corrosion between these plates causes them to seize, resulting in a bouncy ride that can damage the boat's hull or the trailer's welds.

Apply a dielectric grease or a lanolin-based electronics protector to the trailer plug and the light sockets. This prevents the 'green death' (oxidation) that causes flickering lights and blown fuses in the tow vehicle.

Use a torque wrench to check the wheel nuts (typically 125Nm for steel rims). Vibration from corrugated coastal roads can loosen hardware over time. Check the U-bolts securing the axle to the springs for any signs of movement.