Rustproofing Your Vehicle

Rust is a fact of life with any 4×4, especially for those utilised for their intended purpose of off-road use, but even Chelsea Tractors are not immune to chassis corrosion. There are many factors which determine a vehicle’s propensity to rust and the first problem is actually on-road use. What happens every winter here in the UK? Total confusion and sheer stupidity once the icy mornings appear. Instead of waking earlier, people simply get up as normal so don’t allow time to defrost their vehicles, or allow extra time for their journeys as they still act like it is summer.

Corrosion due to rock salt can be widespread, chassis rails are particularly susceptible on 4x4s. A regular inspection would have highlighted this vehicle’s problems a lot sooner.

We also get councils waiting until the last moment before they send out their gritters, because lorries consume diesel, suffer from wear and tear, plus of course there are the gritting and support crews to consider. All this costs money which understandably councils want to minimise as much as possible. Then it’s all hands to the pumps as they get the gritters into full swing, throwing tonnes of that horribly corrosive rock salt all over the roads. Of course we as 4×4 drivers have our more open treaded tyres, so pick up and blast the underside of our vehicles with this nasty rock salt. With so much rock salt being thrown around it is Sod’s Law that some will get inside any drain holes or any other openings in our chassis, plus any other openings on the underside of our vehicles.

Next we get rain and the big thaw (very often accompanied by flooding), so the damp and wetness from these also get into our chassis. This in turn dilutes the rock salt into a highly corrosive saline solution which runs down and around our chassis, venturing into any other openings or voids, and when they eventually dry out, we’re left with a nice coating of salt covering our vehicles; not good!

Rust can ruin your day, the owner of this U.S. specification Toyota Tacoma can vouch for that.

Next we get the off-roaders – the hobbyists who cover this layer of salt with mud, which is perfect for holding salt in contact with the metal. Same and worse is true of the ‘working 4×4’ such as vehicles used in the farming or forestry industries as just two examples. They get many more corrosive entities inside their chassis or other voids, hence corrosion is even more likely.

Chassis Cleaning

Chassis cleaning both externally and internally is a the crucial factor in effective rustproofing, as you have to get rid of all the accumulated salt and mud in the chassis and voids to stand even half a chance. To do this a hosepipe is good, but a jetwash is better, this is where to begin. This task is best undertaken in winter or wet conditions, as the mud is soft and a hosepipe on a jet setting is effective in removing wet mud. This is okay, but as mentioned, a jetwash is much better. Blast the inside of your chassis with a hosepipe or jetwash to remove the mud and any salt trapped underneath it. Also blast through each end of the chassis rails and through any holes such as drain holes you may have. You’re quite likely to be surprised just how many holes a chassis has. Blast through then all in as many directions as possible until any water draining out is clear.

Next the chassis needs drying and this means internally, as most unseen rust and corrosion is internal. If you were observant when cleaning your chassis, you may have noted the corrosion you washed out as loose rust or chunks of rust.

The results of tin worm on a Jeep chassis.

With a dry chassis you need to clean out any remaining mud. This isn’t as difficult as many people imagine. One method is to use a thick Bowden cable or wire rope with sufficient length to reach past the centre of your chassis as you prepare it for action. You take a piece of heat-shrink tubing and shrink it onto your wire rope about 4-6” (100-150mm) from one end of the rope and shrink it down firmly, you take the 4-6” end of the wires and open them out until they are a tight fit in your chassis rail and insert this birds nest of wire into your chassis rail. On the other end you attach a drill by putting the end of it into the chuck and begin turning it while pushing it into your chassis rail and this will abrade it and remove any remaining mud and rust. Repeat this process from the other end of your chassis rail, and then repeat on your other chassis rail until they are clean. Remove your cleaning rope and burr the end again and shape it into a shape similar to your chassis rail, but larger, and insert it again and use a drain rodding motion to clean out all of the corners of the chassis rail. Blow out with compressed air and you are ready for rustproofing.


Basic Oil Rustproofing

If you have access to a compressor and a paraffin gun you can do basic rustproofing using old engine oil. You thin the old engine with gun wash thinners or petrol and put it into your gun and inject the chassis rail. Fire plenty of this thinned oil inside the chassis rails and always aim for the top of the chassis rails so any surplus will run down the sides and coat the bottom of the chassis rail. You will also need drip trays or containers under any drain hole or opening to catch anything running out. This drained oil can be filtered by putting a set of the wife’s tights or similar, over a funnel and the drained oil strained through it into another container for reuse.

The real key to success using old engine oil is to absolutely lather the insides of the chassis rails with oil and use a combination of spray and mist so everything inside is covered. Realise you are going to get a lot of drainage, you can never use too much but you can use too little.

You can use new oils if you like, as engine oils are cheaper than manufactured rustproofing kits. New gear oils can also be used if you have access to them, but you will need to thin out thicker oils more.
Manufactured Rustproofing kits/components

There are many rustproofing kits on the market along with many individual components of these kits, but before you even consider using them you have to take extra care in your cleaning. A degreaser need to be used to remove any grease or oil prior to using a manufacturer’s kit. You begin by spraying a degreaser inside your chassis and jet wash it off, then you use a steam cleaner as the heat of the steam really cleans off any grease or oil the degreasing has missed.

  Photo: Dinitrol UK

Here in the UK the two main rustproofing suppliers are Waxoyl and Dinitrol and both have a long tradition of effective rustproofing, but my preferred choice is Dinitrol as their range of products is much larger and more effective as they have better “creep” in their products. Creep is where two components are connected, usually by welding or spot welding and the tight gaps are still gaps which will rust in between them. Dinitrol products seem to penetrate small or tight gaps better than Waxoyl and Dinitrol do products specifically designed for “creep” which will get into these gaps. As they are all compatible products you can use a Dinitrol product designed for creep and then overcoat with another product. 

Photo: Waxoyl AG

Both manufacturers do a range of applicators for DIY and professional use and often they are worth considering as the applicator wands can get into chassis rails and other cavities using the smallest holes, but you don’t really need the full kit so buy what you will use and save money.

Apply the rustproofing in accordance with the manufacturer’s instructions and cover the ground beneath the area being treated, as rustproofing often runs out or it splashes. Take my word for it, removing rustproofing compound from your drive or garage floor is a pig of a job, so avoid it ever reaching the ground.

In some instances, especially with Dinitrol, you may begin by injecting a thinner product to allow it to creep into joints and cavities, and then go over this with a thicker product to put a heavier coat onto the bare, cleaned metal to give it a covering over the thinner product. In both instances the vehicle needs to be left for the prescribed period of time for the solvent to evaporate.

How often should I do my vehicle? In most cases for most 4x4s they are best done every 3 years by applying another overcoating of your chosen product.

Photo: Krown UK (also thanks for this article’s lead photo). Here are Krown’s ‘here & after’ shots of their preventative corrosion treatment.

There are of course professional companies that will provide rust prevention for your vehicle. Two such companies are Ziebart International Corporporation based in Troy, Detroit, Oakland County, Michigan, U.S.A (BLG Autotec Gmbh & Co. KG being their agent in Germany) and Canadian Krown Dealers Inc. Schomberg, Ontario, Canada (agents in Belarus, Czech Republic, Denmark, Estonia, Finland, Kaliningrad (Russian exclave), Latvia, Lithuania, Norway, Russia, Sweden, Ukraine, United Kingdom). Krown Rust Control Ltd. in Dudley, West Midlands, England are Krown’s British dealership.


Many newer 4×4 pick-ups have had their chassis quite literally ‘snap in two’ due to a flaw in their original design, and a lack of quality in the steel used in their construction. There have been numerous cases of their chassis snapping when loaded, Nissan products seem the most affected but other 4x4s are affected.

Due to their inherent structural problems, and internal or external chassis problems, corrosion is to be avoided at all costs as this will weaken an already weakened chassis and it is liable to crack and ultimately snap; it would be prudent to clean these chassis rails out and treat them every year.

Strengthening your chassis rails is also possible. Aftermarket strengthening kits are now being produced for Nissan Navara pick-ups for example, these being sourced via Richy Holmes – 07946 663091. He will inspect and repair your chassis with 5mm thick plates.

Stage 1. Clearly this Nissan has seen better days. Yes it’s an older model, but even D40 models barely six or seven years old have experienced the same fate.
Stage 2, a stress crack appears. Judging by the photo, granted there is very little in the way of rust, but it seems that many chassis rust from the inside out – thus weakening the inferior quality steel.
Stage 3. These are the Navarra strengthening plates as produced by Richy Holmes.
Stage 4. Plates now welded in situ, it’s obvious even with corrosion, the chassis has a fighting chance of surviving a few more years.
All the rustproofing in the world was never going to save this poor ol’ relic, but in the fight against Fe2O3 (rust) it’s a case of ‘every little helps’.

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Tom McGuigan