The exterior of a car will look great, but you can’t overlook the importance of the undercarriage. Even if the vehicle does nothing but shine, it still might be suitable for the junkyard.
Regarding the general technical inspection, a rusted underbody is one of the most important criteria.
Corrosion protection of the underbody and sealing of hollow spaces are the only surefire ways to prevent rust damage to the wheel arches, side skirts, and underbody over the long term.
Unfortunately, neither of these measures is long-lasting, and older vehicles require more frequent inspections than newer ones. Protection against underbody corrosion is the topic of discussion in this article.
You will obtain all the information you require concerning the expert sealing of your vehicle in this location.
A combination that should not exist
Sheet steel is still the primary material used in automobiles today. No other material comes close to matching the advantageous strength-to-cold deformation ratio that this one does at an affordable price.
However, sheet steel has a high iron content, which can be a problematic factor. In the worst-case scenario, iron will begin to rust when it comes into contact with moisture and de-icing salt.
Corrosion will continue if this problem is ignored for an extended period.
Protection from underbody corrosion is helpful, but it won’t last forever
It is a thick, sticky, bituminous protective agent that does an excellent job sealing sheet metal.
New automobiles produced in today’s market come with an extensive protective coating applied at the factory designed to last for several years.
The corrosion protection for the underbody is typically applied at a thickness of approximately half a millimeter. In addition, the rubbery material absorbs impacts from gravel and pebbles very effectively and does not scratch.
On the other hand, underbody corrosion protection loses its effectiveness over time. After eight years at the latest, the protective coating should be thoroughly checked. If it cracks or flakes off, action must be taken immediately.
Be careful; outdated corrosion protection can develop rust!
The underbody corrosion protection system has one major flaw, and that is that it practically traps moisture.
If salt water seeps in between the paste and the sheet metal, it will be impossible to escape.
Rust damage is inevitably caused when water is allowed to stand on sheet metal. As a result, an outdated protective coating can even serve the opposite function of what it was designed to do; rather than preventing corrosion, it can promote the formation of rust.
Renovate and repair the protection against corrosion under the body
It won’t accomplish much if you try to fix the damaged protective coating with some new spray bitumen.
The old anti-corrosion coating must be stripped off to prevent rust from forming on the car’s underside.
The unfortunate news is that this can be very time-consuming or expensive. However, there is some good news as well.
It is only necessary to repair the areas that are severely damaged. Most of the time, these are the edges of the skirts or the wheel arches.
On the other hand, the sealing of the central area of the vehicle is typically designed to last for the entirety of the life of the automobile.
Procedure for removing the protection against underbody corrosion
When removing the underbody corrosion protection, three different methods are taken into consideration:
1. Extraction by hand using a putty knife and a brush
2. Burning
3. Sandblasting
It is very laborious to remove putty manually with a putty knife and brush. This method is ideal for removing cracked or otherwise damaged components that have become loose. A machine would not be beneficial in this location.
The thick bitumen quickly clogs rotary brushes and sandpaper, making it difficult to do the job. Therefore, one has no choice but to put in significant effort.
Using a heat gun can simplify the task, particularly in areas that are difficult to access. The act of burning is essential to the operation of specific hardcore mechanics.
However, we cannot stress enough how strongly we advise you to avoid using any methods that involve playing with fire.
If you choose to proceed in this manner, there is a high probability that you will first catch the car on fire and then your entire workshop.
In recent years, sandblasting has emerged as the technique of choice for removing underbody corrosion protection.
Here, we make a fundamental distinction between two distinct approaches, which are: the abrasive method and (em, strong) the (em, strong) non-abrasive.
Abrasive sandblasting uses a solid granulate that is accelerated with pressurized air and then blasted against the underbody of the vehicle to remove rust.
Sandblasting is the method that is most widely used. However, in today’s world, in addition to these methods, a wide variety of other options are also available, such as baking soda, glass, plastic beads, walnut shells, and many more.
The fact that this abrasive procedure always produces satisfactory outcomes is a significant strength of the case for using it.
It enables the removal of the previous protective layer speedily and thoroughly. In addition to that, it is a method that is reasonably priced.
However, a large amount of dirt produced as a byproduct of abrasive sandblasting is one of the process’s drawbacks. The pressure that is too high and the use of an inappropriate material are potential causes of damage to the excellent floor of the vehicle.
An effective alternative is using a method of sandblasting that does not involve the use of abrasive materials.
Dry ice, composed of frozen granules of carbon dioxide, is often used in place of working with more traditional hard materials.
When these granules come into contact with the corrosion protection of the underbody, they spontaneously disintegrate, effectively removing the substance.
A negligible amount of dirt is also produced, except for the remnants of the protective layer, and this dirt does not cause any damage to the floor in any way.
The use of high-pressure water jetting is another option that can be considered for its lack of abrasiveness.
These very effective procedures have one significant drawback: they are pretty pricey.
The daily rental fee for a dry ice blasting device typically ranges between one hundred and three hundred euros.
It is strongly recommended to carry out this procedure on high-end vehicles, such as luxury sports cars or historic automobiles.
Dry ice blasting can carry a price tag of between 500 and 1,000 dollars when performed by a professional service provider.
Elimination of Rust
Some preparatory work still needs to be done before the new underbody corrosion protection can be applied.
In particular, all rust must be removed before the new protection can be applied. You can get quite far with a spatula and brush; however, this will only remove rust stains on the surface that are loose and flaky.
You can access deeper parts more efficiently with an angle grinder, but you will permanently remove some of the excellent material in the process.
As a result, we advise that you use a brush to apply a rust converter in this area and then let it sit there for some time so that it can do its job.
If the reddish rust has transformed into a black oily film, then it can be easily removed with a rag because the film is oilier. Welding can, of course, be done on the rust holes.
It is essential to clean and cover the surface.
For the purpose of protecting the underbody from corrosion, the same criteria apply to any sheet metal coating.
Degreasing the part is a prerequisite to applying the coating, so do that first. It should also be mentioned that silicone cleaners have proven to be the most appropriate method.
The substance is spread evenly across the entire surface, allowed to take effect, and removed.
However, once this process is complete, it will no longer be possible to touch the bodywork. It is also now against the rules to use WD-40 or to penetrate oil because if you did, you would have to degrease everything again.
Underbody corrosion protection may NOT be used to cover any moving or hot parts of the vehicle. As a result, it is strongly suggested that you wrap the mechanism that controls the steering and the exhaust pipe in the newspaper.
When corrosion protection is applied, the steering mechanism might become less mobile, and the exhaust pipe might become more of a fire hazard.
Therefore, exercise extreme caution in this situation. Additionally, cover the exterior of the side skirts up to approximately half their length. Protection against corrosion ought to be applied there as well.
Enhanced protection against corrosion
If the underbody was really polished to the sheet metal underneath, you should seal it with a sprayed primer coat. If not, you should not polish the underbody any further.
This will result in better adhesion of the corrosion protection. The first coat of primer is applied by simply spraying it on and letting it dry.
Today, corrosion protection for the underbody is applied in the convenient form of aerosol sprays. These sprays are sprayed onto the sheet metal to generate a strong layer with a thickness of approximately 0.5 millimeters.
In most cases, applying an excessive amount has no positive effect. The greater the thickness of the layer, the more material it throws away.
The new protective coating must be allowed to dry for approximately four hours. After that, you will be able to peel off the layers.
The remaining portion of the skirt’s exterior can then be varnished to match the color of the vehicle. The underbody corrosion protection is intended to be painted as soon as it has hardened, which is made possible by the component’s design.
