One of the biggest challenges, and reasons for restoring a Land Rover, is to repair corrosion and rust issues. Due to the dissimilar reaction that aluminum has with steel, areas where the two metals meet tend to be the most problematic. This page provides a peek into where these issues crop up, and how we make repairs that last.
The rear x member on a defender is usually one of the first areas to become rusty. It is a fairly complex shape made with different layers of metal. Where the two layers of metal meet, they are spot welded or are plug welded together. When moisture, water, dirt, road salt, etc get in between these layers, where there is usually no paint, corrosion begins to rapidly occur.
There are several ways to fix the issue depending on how severe the rust is:
As previously mentioned, the rear x member is usually the first place to get rusty but there are some other trouble spots. There is a hole that is frequently hidden where the removable gearbox x member bolts on. When moisture and salt get trapped between the two layers of metal they rust as well. Cutting out the rusty section and putting in new steel can fairly easily repair this. Where the catalytic converters are positioned beside the chassis can often have a hole. The extreme heat of the cats burns off the paint & the steel becomes more susceptible to rust. The mid x member that the rear A frame mounts to also has numerous gussets and flanges which trap dirt and salt which promotes corrosion too. This is an awkward area to repair with the body on and if the rust has gotten in this far, it usually condemns the chassis. Just forward of the rear fuel tank where the chassis swoops down can also be a collecting point for dirt and salt inside the frame. Again, if this area is really rusty the frame is not worth saving.
The ultimate solution is to replace the entire frame (chassis). With the rear x member being the first corrosion point on the frame, and the rear x member is rusty to the point it needs to be replaced, will usually know by this point there will be additional problems elsewhere in the frame. New frames are usually galvanized and so they start with a much better level of rust prevention. To increase that level further they can be painted & waxoyled as well.
When aluminum and steel are sandwiched together in some circumstances there can be galvanic corrosion. The galvanic corrosion of aluminum is usually mild, except in high saline situations like road salt and seawater. The defender doors provide the perfect environment for this type of corrosion. The frame is steel & the skin is aluminum. The frames only have a thin layer of primer on them before they are bonded and crimped to the skin. There is no seam sealing or other method to keep the moisture and salt out. The aluminum typically corrodes first from the inside out & manifests itself as bubbles under the paint as moisture travels through the pinholes in the aluminum causing the paint to bubble.
The 4x4 Center’s solution is to build defender doors in stages is as follows:
The steel chassis bolts directly to the aluminum rear body. This is another area where the galvanic corrosion between the steel and aluminum happens quickly; likely because it gets covered in a lot of road grime. Our solution is to paint the chassis x member and the rear body with them completely separated. When they are bolted back together a plastic washer / shim is put between the steel & aluminum to keep them completely separated.
The firewall & the chassis make up what we call “the backbone” of the defender. Both are steel. The firewall is susceptible to rusting because there are so many cavities & layers of metal that trap moisture & salt. In the foot wells, which get blasted with road grime, each corner is made up of a spot-welded double layer of steel. The rust starts inside of this sandwiched double layer of steel that isn’t painted, and the rust starts. Eventually spreading further as the paint cracks & starts to fall off.
Our solution is to repair or replace the firewall depending on what is most cost effective, galvanizing, painting, seam sealing, and waxoyling as we do so. The advantage of galvanizing is that the zinc gets into the seams and cavities providing protection where paint cannot. Galvanizing a firewall is not easy, the heat and weight of the zinc can easily turn he firewall into a pretzel. Painting galvanized metal and actually getting the paint to stick is another area things can go wrong if the proper procedures are not utilized.
The original defenders had a galvanized body capping. Around 1989, Land Rover started painting the body capping, body color, and stopped the galvanizing. It appears that the body capping & the rear body have a thin layer of primer on them when they are put together, and then they are painted body color. Rust tends to start on the underside of the capping where there is just primer. This then causes the paint to start flaking off on the outside & also causes a dissimilar metal corrosion on the aluminum rear body. We galvanize the capping & paint them inside & out with primer & color. We also paint the rear body with primer & color prior to reattaching the cappings. That way, both the aluminum and steel have far more protection against corrosion, and there are more layers of protection to separate the aluminum and steel.
As all of the above are mounted right on the back of the defender they are subjected to a lot of road grime and salt and are usually pretty rusty. The 3rd brake light mount is made of light gauge steel tubing, and is often completely rotten. We make our own duplication of the original. Usually the rear step is salvageable and the tire carrier is just surface rust. While the step and brake light mount get galvanized and painted, the tire carrier gets painted.
Prepping for galvanizing is important as these tubular sealed parts need to be pre-drilled for the zinc to enter, and leave the tube, allowing for gas expansion due to the heat.
As with most vehicles these lines are made of steel and get rusty (diesel defenders had plastic lines). Any restoration we do receives a set of stainless-steel brake lines and fuel lines, made to be the same shape and fit as the originals that, will essentially last forever.
Open and regular communication is the key to all of our successful projects. At the 4×4 Center, we make sure it’s smooth process that puts you into the vehicle of your dreams.
Learn to get the most out of your Land Rover at The 4×4 Center Driving School. Check out the challenges that await you at our 1,100 acre facility in Bolton, Vermont. Use one of our vehicles. It’s a fun, educational experience you’ll never forget.
The 4x4 Center is a World Class Land Rover Restoration facility located in South Burlington Vermont, known for North East Land Rover Repair and East Coast Land Rover Restoration and, is in no way affiliated with Jaguar Land Rover of North America.