Rust Proofing Your 4WD: How to Avoid Corrosion Offroad

Let's be honest, 4WDs are not cheap these days. Along with regular servicing and general maintenance keeping it free from contaminants that will lead to rust is one of the best things you can do in terms of maximising the lifetime of your rig and getting the most value from your investment. This is even more important for those of us who drive on the beach regularly, or even go off-road as often as possible. You don't even need to drop it into low range, living within cooee of the coast is enough for rust to sink its flaky brown teeth into your vehicle.

The Number One 4WD Rust Prevention Tip

The best thing you can do to prevent rust and corrosion, hands down, is keep your vehicle clean. Having a regular washing schedule means that mud and wet sand cannot create the sealed, moisture-retaining environment that rust thrives in. Basically, rust forms when oxygen and moisture react with the iron in the steel in your 4X4's panels and chassis.

By having a layer of salt or grime covering the panel surface the moisture and oxygen cannot escape, so they slowly begin to react with the steel underneath. Next stop: Rust-town. Regular and thorough cleaning prevents this layer from ever being formed and makes corrosion forming much more difficult.

Why 4WDs Rust Faster Than Road Cars

4WDs are, by their nature, vehicles that are much more likely to get up close and personal with Mother Nature. They're driven through mudholes, through dusty and humid environments and on the beach, where sand and salt combine with the moisture and oxygen to create a sort of corrosion supercharger. These are the sort of environs rust absolutely thrives in.

Anywhere near salt water in particular is particularly dangerous, and even if you're not a cowboy who thinks driving through the surf at low tide is clever (it really isn't) beach sand is comparable to seawater, which is something not too many folks realise.

Couple that with a few small scratches or impacts on the paintwork, allowing the contaminants access to bare metal and rust can form quicker than it took you to read this sentence. Even just living near the coast can accelerate the process.

Where Rust Usually Starts on a 4WD

There's no shortage of areas where rust can form. Many are model specific (60 Series Land Cruisers in the roof turrets, Suzuki Sierra sills, GQ Patrol sliding window frames) but all 4WDs are vulnerable.

Chassis Rails and Cross-Members

Frames are hollow and overlooked during a normal washing. Couple that with a few mud holes and a sand bogging or three and it's perfect for trapping moisture and contaminants.

Suspension Components and Spring Hangers

Shock rod chroming can flake off, particularly after an impact and the steel underneath begins to pit and corrode soon. Similarly to chassis rails, many suspension parts also do not allow easy escape for water and mud and filth, which isn't a great combo.

Diff Housings and Axle Tube

Diff housings aren't immune either. There are surprising amounts of nooks, crannies and perpendicular edges for a seam of paint to lift and for the damp and grit to accumulate.

Door Sills, Pillars and Body Cavities

Doors and cavities are fitted with drain holes to allow water that has inadvertently made its way in to escape. Sand and salt and water get in, the drain are left in and before you know it your vehicle is rusting from the inside out.

Your Rust Protection Guide

Before Your Trip

One of the common mistakes we see is people applying spray-on protection from salt and dirt, like lanolin, before a trip. While lanolin is an excellent corrosion inhibitor it can actually act as an adhesive for sand and salt, trapping it against your vehicle, which is the last thing you want. You're much better off starting with a clean and dry surface before heading off-road. Having a rust preventative coating applied a few days previously can also help a lot. This will give you the most effective set-up for the more important post-wash after returning home from your trip.

After Your Trip

The rule of thumb is if you've been on a day trip then wash your vehicle the afternoon you get home. If the day trip has run late, then the next morning. As long as it's within 24hrs of salt or mud exposure. We've previously covered how to wash your vehicle in detail, but the key is to not only get the surface panels but also underneath the vehicle. Chassis rails, suspension components, diff housings and wheel arches are all musts. Investing in some quality Salt Shift Underbody Blaster and Chassis Flusher is money well-spent. A great tool for properly rinsing the underbody is the garden sprinkler, or if you're feeling fancy, one of those sprinklers that runs around on a track.

Underbody Coatings and Sprays: What Works and What Doesn't

First things first, dousing your rig in all of the underbody coatings and sprays will help, but they only really work on pre-cleaned surfaces. The post-trip wash is paramount and can't be adequately replaced by anything in a can.

Do Underbody Spray Coatings Work?

There are several options for underbody sprays that leave an impenetrable hydrophobic barrier on your steel that prevents dirt and moisture from being trapped and rust forming. Some people swear by them, and others are more sceptical. Most of these products' efficacy will come down to factors like how much beach driving you do, where you live, how often you reapply and how fastidious you are about cleaning your 4WD after going off-road.

While you cannot rely on one product to prevent rust completely, quality corrosion inhibitor sealants can help a lot for vehicles that have a high exposure to rust-friendly conditions.

Do Lanolin and Fish Oil Actually Prevent Rust?

These were probably your grandad's favourite methods for preventing rust, and it's a fair call. They work and have a long history of doing the job. However, there are a few downsides. They tend to create sticky surfaces, which sand, salt and grit can become glued to, which isn't ideal. They also need regular reapplication and can quite easily be rinsed off inadvertently.

Electronic Rust Prevention Systems

The idea behind these gadgets is by running a small electrical current through the metal prevents rust from taking hold. The science actually has merit and they do work, despite many folks in off-road circles claiming otherwise. The truth is, they are a legitimate means of rust prevention, but they're relatively expensive and like all the others they cannot be solely relied on to keep your steel unmolested. Regular cleaning is still king.

Rust Proofing an Older Vehicle

Rust is porous and draws moisture deeper into the metal it's started on. With older vehicles the surface rust you can see may actually just be the tip of the iceberg of what's hiding underneath.

This is why early action is key in preventing serious and costly damage. If you've bought an older vehicle with signs of surface rust, going around the whole rig with a magnet is a cheap and easy method of finding out how severe the rust patches are. If the magnet doesn't stick to the steel chances are the whole panel is toast.

It's important to be realistic with older 4X4s. They absolutely can be protected but it's a lot cheaper and easier to deal with some light surface rust than a panel that's riddled with metal cancer.

What to Do If Rust Is Already Starting

• First determine what you're dealing with. Surface rust on a panel is a lot easier to deal with than deep-seated structural rust in a chassis rail, spring hanger or body mount.
• If it's light surface rust then you have several methods to handle it. Mechanical removal, rust converters and recoating are probably the most common steps.
• If it's deeper and has taken a hold of structural members then it's time to start cutting out the effected metal and welding in new sections of fresh steel. This is usually best left to professionals as they have the assessment and practical experience to determine what the best course of action is.
• For a huge range of rust prevention and car care products, make sure you head on over to Superior Engineering's Car Care Range. We've got all of your pre and post-trip cleaning needs covered!

Rust Proofing FAQs

How often should I wash my 4WD after beach driving?

Every time, as soon as possible. Ideally within 24 hours.

Is lanolin still worth using on a 4WD?

Yes, but it doesn't replace regular washing and can create a sticky coating that actually traps contaminants. It's great for inside cavities, electrical connections and moving parts like door hinges.

Can you rust proof a vehicle that already has surface rust?

Yes. You have multiple options including mechanical removal, rust converters or special coatings that can arrest the rust's growth.

Do bash plates help prevent rust?

They're a double-edged sword. They can keep a lot of splashes and debris out of the underbody, but they can also trap mud and salty water where you don't want it. They're certainly better to have than not, but not necessarily because of their rust-protection qualities.