Undercoating a car makes sense if your car has little or no rust protection at all. Furthermore, it makes sense to undercoat a car if your car is a bit older and valuable as some older cars are more likely to be plagued by corrosion.
Secondly, undercoating a car makes sense if you live in a climate with a lot of moisture, salt, and unpaved roads. As far as BMWs are concerned, it’s a good idea to undercoat a BMW if the factory rust protection warranty has expired or has been voided.
BMW goes to great lengths to ensure that the rust protection is as good as it can be, and because of this BMW offers a 12 year-long rust protection warranty for cars built after 2004. Besides this, BMW is no different from any other car out there, and correctly applying undercoating to any car is a good idea.
There are a few different ways one can protect a car from rust, and getting to know each of them is paramount. Drip oil spray seems like the first go-to option, but tar undercoating and electronic module solutions are also fairly common.
Undercoating on a new BMW
If you bought yourself a brand-new BMW, first off, congratulations! Secondly, no, there is no need for any additional undercoating on a brand-new BMW. As mentioned previously, BMW offers a dedicated 12-year-long rust protection warranty for every car that has left the factory after 2004.
BMW rust proofs their cars extensively. The process begins by dipping the entire chassis and body panels into a special chemical bath which consists out of manganese, phosphate zinc, and nickel. This also cleans the panels extensively, and after that BMW electrically charges the entire car which should in theory make it impossible for rust to occur.
After the so-called e-coat is completely dry, a set of sophisticated robots apply a bunch of sealant solutions into all the nooks and crevices. BMW also applies a thick protective layer onto the underside of the car as well to make sure that there are no chances of rust spots appearing.
If you consider all of this, there is no need for rustproofing a new BMW, especially so if it may also even void the factory warranty in the process.
Undercoating a used BMW
Undercoating a used BMW, one that is no longer protected by the 12-year-long warranty might seem like a more reasonable idea. Especially so if you live in a climate with adverse weather conditions, lots of salt, unpaved roads, or you plan on keeping the car for years to come.
The car needs to be cleaned comprehensively before the undercoat is applied. An undercoating job usually costs less than $160, but if you are using a premium undercoating solution, and the work is being carried out by trained professionals, it may even cost a bit more.
It is paramount that the undercoat is applied by a professional onto a clean surface because failing to do so might even worsen the situation. This means that if the undercoat is not applied correctly, it might crack prematurely, and collect moisture between the coat and the vulnerable parts of the body.
You should also consider drip/dripless oil sprays and dedicated electronic modules. Drip and dripless sprays are fairly similar, but the drip version is better because it does not require any drilling or disassembly. An electronic module is a small device that sends a constant current throughout the car and should theoretically stop the car from reacting with oxygen and moisture.
Things to keep in mind when deciding about undercoating your BMW
First of all, don’t undercoat your BMW if it is covered by warranty, second of all, don’t do it if you don’t plan on keeping the car for a long time, or in other words, do it if you plan to keep the car for a long time. If you live in a country that experiences lots of moisture throughout the year, then go ahead and apply some form of rust protection.
Furthermore, if your country experiences lots of ice during the winter, and your country also uses salt as an ice deterrent, make sure to wash the car regularly as salt accumulation is known to cause rust spots. Cleaning your car inside out also makes it a lot harder for rust to appear.
If you also opt for paint protection film or a dedicated ceramic coating, rust is also less likely to happen. If you do all these things and don’t plan on keeping the car for a very long time, there is no need for any additional rust protection, but if you want to have peace of mind, go ahead and do it.
When can I wash my car after the undercoat has been applied?
It is highly recommended that you wait at least 48 hours before you start washing your freshly rust-proofed car. Even after 48 hours, you should not use any degreasers on the underbody of the car, and try not to splash the coated area with hot water too much.
You should also avoid using a dedicated pressure washer on the underside of the car for a few days as well. Some coatings take more time than others to harden, so be sure to read the label before trying to wash your car.
How often should I undercoat my car?
The perfect time for undercoat application is spring, and you should repeat the process every year. Some undercoating solutions might even last a bit longer, some of them can only offer a few month’s worths of protection.
Be sure to gather all the relevant information about the coating you are using before deciding when you should re-do it. An opened premium can of undercoating has a shelf life of up to a year, and some affordable ones only last a month or two.
Should I wash my car before rust-proofing?
Yes, you should. It is recommendable that you wash your entire undercarriage with a pressure washer thoroughly. You should also use a bunch of degreasers to completely clean out as much dirt as possible.
If you don’t, the dirt can get stuck between the coating and the panel which might even result in unwanted cracking of the coating. This is especially important if you have any salt residue on the underside of your car.