Should I wash my car before rust-proofing?

Washing your car before rustproofing is extremely necessary because if you don’t remove all the contaminants from the surface, they might even worsen the situation.

This means that all the dirt and grime could potentially get stuck between the undercoat and the panel itself and even cause or progress corrosion. A nice thorough wash before applying an undercoat is essential, and should never be skipped nor taken lightly.

Whenever you apply any kind of protective layer such as an undercoat, wax, paint protection film, it’s always best to have the car completely detailed and cleaned from all the contaminants. By not doing so you are also lowering the lifespan of all protective layers.

After you’ve rust-proofed your car, it takes 30 minutes for the undercoat to harden, but you do have to wait at least a day for the coat to fully dry. It’s also recommendable that you always skip washing the underside of your car with degreasers or high-pressure washers.

Coating preparation

After you’ve decided to undercoat your car, you first have to gather all the necessary equipment. A pair of protective goggles and gloves are essential as lots of these coating solutions are highly toxic and can even damage your eyes or skin in direct contact.

Furthermore, make sure you have a balanced car hoist that can easily manage the weight of the vehicle as you will need all the clearance you can get. Before doing anything, make sure you wash the car with a high-pressure washer to remove all the hardened contaminants.

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After this, you should use a high-quality degreaser before grinding out any possible signs of corrosion. Proceed with using sandpaper to completely smooth out the surface. It’s also a good idea to use an air compressor at this point, just to remove all the small remnants of metal.

Go through all the nooks and crannies and completely inspect the underside for any signs of rust. Make sure you also have a powerful flashlight so you can inspect the surfaces more efficiently.

Coating application

After you’ve finished cleaning any possible signs of rust, make sure to wash the car down once again, and let it dry. It’s essential that there is no moisture left on the surface and a high-pressure air compressor gun should do the trick.

Prime all the areas you’ve grinded, and paint them with automotive-grade paint. After the paint has completely dried, you are ready to apply the coating. Use smooth and slow hand motions whenever you spray any kind of high viscosity liquid.

Spray the coating evenly and try to make sure you are not over-spraying onto any non-metal surfaces. If there are many non-metal surfaces such as electronics, tape them out. You can use either a spray can or an electric sprayer for this process.

It’s always best to stay 6-8 inches away from the surface while spraying. After you’ve finished applying the first coat, let it dry completely (approx 30 minutes, check the can label). Then go ahead and do the second and final coat and wait for it to dry.

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Coating removal

No matter the price or application, no undercoat can last forever. Most undercoats are replaced every year even though some of them might even last a year or two more. Make sure you read the can label and consult yourself online about the specific product you are using.

There are a few different ways one can remove a coating. Using a wire wheel is a fairly common method of coating removal, especially so if the coating is extremely durable. This process is better left for the professional, but if you know what you are doing, then it shouldn’t be much of an issue.

Some car shops often use dedicated air scrapers to remove paint, coatings, glue, or rust without damaging the metal underneath. Obviously, most people don’t have an air scraper lying around, but if you do for some reason, you could use one to safely remove tar-based coatings.

But if you want to remove the coating yourself as easily as possible, you can use a scraper and a hairdryer. First, you should heat the area until the coating starts softening and remove it gently. You can also use dedicated coating removal solutions with a scraper, and both of these are very effective ways of coating removal.

FAQ Section

Should I wash my car after rust-proofing?

You should wait a while before you start cleaning the car as coating takes some time to completely harden. You could lightly wash the car after 24 hours of coating application, but don’t use any aggressive chemicals nor high-pressure washers on the undercarriage itself.

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You should also skip hot water for a few days as well, as hot water can potentially soften up the coating prematurely. Even after a week or two, you shouldn’t use aggressive chemicals such as an industrial degreaser on the coated surface.

What should I do after I undercoat a car?

If you’ve done it yourself, first of all, congratulations! Second of all, wait for it to dry before driving it, a day or two should do the trick. After a day or two have passed, go ahead and take the car in for an inspection.

Lots of body shops are fairly familiar with rust proofing and they can easily tell you if you’ve done it successfully or not. Try to take the car in for an inspection as soon as you can. Doing anything right the very first time is rare, and don’t be discouraged to try again.

How effective is undercoating?

It depends on the application process and the product itself. In theory, an undercoat should keep your car safe from rust for at least a year if done properly. You shouldn’t expect these types of coatings to be 100% perfect, and always be sure to check the application from time to time.

But if everything is done as recommended, tar-based coatings are effective enough. These types of coatings are one of, if not the most popular way of rust proofing. It’s worth mentioning that 99% of modern cars do not require any additional rust proofing as they are usually very well protected straight from the factory.

Marko Mikulic

Why do you love writing about cars? I love writing about cars as cars are a huge personal interest of mine. I was raised in a car enthusiast community and ever since I was young, I always wanted to do car-related work.

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