Case Studies

Helping Your Car Live Longer – The Truth About Rustproofing and Corrosion Protection

What We Think At Atlantic Motorcar
Talking about rustproofing is much like arguing over which is better, chocolate or vanilla ice cream.
Everyone has an opinion, and everyone is sure their opinion is right. What we are basing our recommendations on are nearly 40 years of European automotive service experience, as well as practical day-to-day observations. 

It’s important to note that what we share here applies to late-model European autos with their excellent and extensive factory rustproofing systems. It’s also important to note that Atlantic Motorcar does not do rust-proofing; we leave that to the professionals who enjoy working with tar and wax. 😉

Our Recommendation For European Autos
We generally don’t recommend aftermarket undercoating on German autos, they are very well undercoated from the factory, and often a second coat of undercoating serves to dirt and moisture, which is not a good thing. Even the oil spray that you’ll often see advertised can do more harm than good. It can damage rubber components if not carefully applied, make a mess in your garage or driveway, and makes it difficult to determine if the vehicle has any fluid leaks when in for service. For Land and Range Rovers, especially vintage models, we do recommend a proper and professional application of the oil-based systems.

Our opinion on rust prevention varies for domestic and Japanese cars and trucks, from washing them often in the winter to keeping them wet with spray oil treatments. See our Prevention section for more details. So for non-European vehicles, read on.

The Exception
The exception to this rule is in case of body damage; in that case, ensure that the body shop caring for your car reapplies a professional rust protection system on the new or damaged sheet metal. When you see a late-model European car with rust, it is almost always a result of accidental damage that was not professionally repaired and protected.

Rust Proofing History
Remember “Rusty Jones,” the iconic character of an automotive rust-proofing chain two or three decades back?
Or the exotic-sounding “
Ziebart“? Probably not, as the big chain rust-proofing shops have largely disappeared over the years as manufacturers have stepped up their factory undercoating systems and metal treatments.

Add in better vehicle design, newer metals, and factory corrosion treatments, with body side moldings no longer held in place with metal clips that promote rust but instead now use an adhesive, and many of the former rust hot spots have disappeared. In fact, our friend Rusty Jones Inc. filed for bankruptcy protection in 1988, claiming that automakers’ extension of factory warranties against rust had caused business to deteriorate.

Better Living Through Design
To better understand the present, it often helps to look to the past. In the early days, cars were just built, they were basic conveniences to get down the road and not expected to last a long time, so little thought was put into durability from a body standpoint, and the sheet metal quality varied widely. Early cars were built on a heavy metal backbone, called a “frame,” with large, heavy components, like the engine, transmission, and suspension, attached to the steel frame. The car body, often of thin sheet metal, sometimes built over wood in earlier cars, served to keep the driver dry in the rain and warm in the winter. And perhaps to add a styling element to the vehicle.

Various types of high-strength steel are found in today’s cars. The blue color is the “crumple” zone, designed to absorb impact energy, and the red is the high-strength steel to build the protective passenger cage.

Today’s cars are very different because the frame system has largely disappeared on most passenger cars and SUVs. Engines and transmission bolt directly or indirectly right to the sheet metal. The body of the car is now not just a structural component that needs to support the engine and transmission but is also a carefully engineered safety system, with crumble zones and various high-strength steel and aluminum parts to protect the occupants.

It’s also become common for manufacturers to use galvanized steel in their vehicle frames. With a zinc coating, galvanized steel doesn’t react with oxygen like iron, significantly reducing the risk of rust. Cars built these days aren’t going to rust out as you’d see decades ago completely. Factors like the climate you will be driving in, the terrain you will be driving on, and the amount you will be driving affect the degree of rust. Rust-proofing will make more sense if your vehicle is regularly subjected to the elements, but if you mainly plan to do city driving in a warm climate, chances are it is optional. Plus, many manufacturers now offer a factory warranty to cover rust and sheet metal perforation, as we read above that our friend Rusty Jones sadly found out.

Rust-Proofing Treatments and Types – Tar and Oil
There are two primary forms of aftermarket rust-proofing today: tar-based spray and oil/paraffin mix.
Both have pros and cons, as outlined below, and it’s important to consider which might work better for you.

Tar Based Sprays
Let’s start with the tar-based spray. You’ll often see this type of coating in cans at your local auto parts store. Also known as “undercoating,” tar-based sprays were introduced in the 1950s to make car ride quieter. Undercoating is an asphalt-based substance similar to tar once it’s dry. It’s 10 to 12 mils thick (think 20 sheets of paper) and acts as a barrier against rust and corrosion by sealing out your vehicle’s underside to protect it from the harmful elements of the road.

The procedure involves spraying a black, tar-like substance on the floor pans, wheel wells, and other exposed parts of your car’s underbody, which then hardens and acts as a permanent shield against moisture, salt, and other elements. Unfortunately, over time moisture can seep behind the hard outer seal and corrode the metal beneath. Furthermore, the rigid nature of a tar-based spray makes it susceptible to cracks, which will pose an entrance for water to get in. For those that choose a tar-based spray, yearly inspections are often required to reduce this risk. Ziebart is one of the largest providers of this method of rust protection. 

Oil and paraffin-based product.

Dripless Oil Spray
Another product, dripless oil, has similar properties to a tar-based spray in that it hardens after being sprayed, creating a moisture seal for your vehicle. Oiling is exactly what it sounds like; it’s an oil-based substance that coats your vehicle’s underside, repelling anything water-based that the road throws to protect it from rust and corrosion. Oil undercoating is extremely thin (think one sheet of paper) and must be reapplied annually to remain effective. It has a firm waxy texture and clings to your vehicle’s frame without any run-off (if very carefully applied).

A dripless oil spray covers more surface area than its tar-based counterpart because it’s applied to more interior regions of the vehicle. Still, this added protection comes with a price. The application process often involves drilling holes into the vehicle’s frame to maximize the area covered. If done by a trained professional, these holes are discreetly drilled and shouldn’t be visible. Additionally, these sprays will often leave smaller crevices, and tight seams on your vehicle unprotected because of their high viscosity. As mentioned, because of the nature of the oil, it does wash off, and it is recommended to be reapplied annually.

How to Prevent Car Rust
My mom said, “An ounce of prevention is worth a pound of cure.”
So how does one go about preventing or mitigating rust if they live in a winter climate?
As you can see, rust on a car can be a very serious issue. This is why learning how to prevent car rust is so essential. Keeping your vehicle rust-free is pretty straightforward. Start with these five tips.

1. Wash Your Car Frequently
One of the easiest ways to prevent rust on a car is to wash it often. Not only will it keep your car looking shiny and new, but it will also remove corrosive debris, salt, and grime. It’s important not to wait for your car to look dirty before washing it. The elements that attack your car’s paint aren’t visible to the naked eye, so by the time you see that you’re due for a wash, some damage has already occurred. 

While any car wash is better than not washing your car, a high-pressure cleaner is the most effective. This will allow you to easily clean tricky areas – like your undercarriage and the inside of your wheel arches. For the best protection, plan to wash your vehicle once a week and have it professionally cleaned, waxed, and detailed twice a year.

2. Don’t Forget the Wax
To keep your car in the best possible condition and prevent rust from forming, you’ll want to wax it at least twice a year. This adds another layer of protection between your car’s paint and rust-causing moisture. If you’re not storing your car in a garage, you’ll need to wax it more often to compensate for the extra exposure to the elements. It’s easy to wax your car on your own, but if you don’t have the time, consider adding a hand wax when you take it for professional cleaning.

3. Protect Your Car from the Elements
Constant sun, rain, and snow exposure can do a real number on your car. If you want to avoid rust, you should park it under cover. If your home doesn’t already have a garage, consider adding one. While a heated garage is excellent, the warmth can speed up the chemical reaction of rust, so leaving it outside in the cold is a good idea after all. 

Common trouble spots on Rovers, but also applies to almost any vehicle.

5. Repair Rust Before It Spreads
It’s a good idea to give your car a once-over each time you wash it.
Keep an eye out for any paint damage or small spots of rust.

Paint chips are easily touched up with inexpensive factory kits, which are small containers with a little brush inside. Every car owner should have a paint chip kit for their car, and there is no better time to check and correct paint chips than after a car wash.

When checking your vehicle, also pay close attention to the condition of any drain holes, water channels, and seals, especially at the bottom of doors. If moisture collects here, rust can start to form unseen.

Any time you notice a possible sign of rust, it’s essential to keep it from growing. Taking care of it before it spreads can save you time and thousands of dollars in future repairs and greatly improve your vehicle’s resale value!

Need More Help?

Questions, or if we can be of help in any way with service on your Audi, BMW, Land Rover, Mercedes, Mini Cooper, Porsche, or other European import, please contact us. Our team of Service Specialists is here to help, for even the newest autos! (207) 882-9969, or you can email our Service Team at

Knowing, not just “doing,” that’s the Atlantic Motorcar Center way.

The Atlantic Motorcar Center Service Team

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