Rust is still a major problem in aging automobiles. Although rust protection has substantially improved with the introduction of galvanized steel during the mid-70s and 80s among all the major auto manufacturers, it is still a problem.
It is particularly a problem in areas where they use a lot of road salt in the winter or brine (a solution of salt and water).
This corrosive element has a habit of accelerating the oxidation process and can quickly do damage to the underbody, wheel wells, and fenders.
Salt acts as an electrolyte that reacts with the metal and has greater volatility than ordinary water alone.
Even the salt in the air can cause harm to paint if you live near the ocean. Oxidation in seasick cars usually begins after about 5 years.
The damage is most commonly incurred when the dew starts to accumulate on the paint surfaces in the morning, thereby, softening and penetrating into the paint.
Acid rain, acidic bird droppings, and tree sap are other catalysts that can penetrate the paint sealed surfaces of metal parts and open up the door for oxidation. For this reason, you need to protect your vehicle with regular waxing and sealing to ward off the effects of oxidation.
There are other techniques available that we can discuss below. However, the first topic is how to repair rust.
Let’s consider this in greater detail, below.
Rust Repairs
No body shop will guarantee a rust repair because oxidation is like cancer.
Even if the automotive technicians do their best to remove the rust, molecular contamination of the metal can convert other metal back into rust by acting as a malignant catalyst.
When moisture penetrates the paint, the process reactivates. Since no paint is totally hydrophobic, the possibility always exists.
Preparation
Before you actually make any rust repairs yourself, you need to have a variety of tools and the proper conditions.
You can expect a rust repair to take the better part of the afternoon if you are also painting it.
Because paint doesn’t set well when it is too humid or too cold, you want the humidity levels to be about 50 percent or less. The temperature should be moderate to warm but not too hot that you will become uncomfortable. Anywhere from 60 to 80 degrees should be fine.
You will also need a clean workplace to reach most rust repairs underneath the car. The best workplace is in a large garage or level concrete or asphalt driveway.
Obviously, you will need appropriately rated jack stands and a hydraulic automotive floor jack if you are going to work underneath the vehicle. You may also need an electric or pneumatic rotary tool and sanding disk for heavier rust that can’t be sanded off easily by hand.
Other Possible Supplies:
- Dust mask
- Chemical-resistant gloves
- Color-matched spray paint
- Primer spray paint
- Clearcoat spray paint
- Rust converter
- Painter’s tape
- Grease and wax remover
- Eye protection/Goggles
- Rust remover
- Clean shop rags
- Paint-prep wipes
Rust Removal
If you are using a rust removal spray for small spots, it is as easy as surrounding the area of the rust spot with a broad margin of painter’s tape for protection. You will then spray or brush on the rust remover. Let it sit a few minutes to work. Then, wipe it off with a clean rag.
When working with rust remover, you will want to wear eye protection and chemical-resistant rubber gloves. You don’t want it to penetrate into your skin because it can be caustic and carcinogenic.
If there is any rust remaining once the area is wiped clean, you can sand it off. Finally, clean it with your grease and wax remover.
Next, you will want to prep the area for paint by cleaning it with a paint prep pad. This will remove any residue left behind. They sell convenient paint prep packets that are for use in small applications near the Bondo in some automotive stores.
Once the area is clean and ready for paint, you will need to seal it with a primer. There are places to order color-matched paint online that also sell a quality sandable primer.
The sandable aspect of it is important because enamel factory paint is usually baked on in layers. Being able to build up layers of primer and sand it smooth can help build a flat and even surface.
Follow the instructions on the can of primer, and let it dry for the appropriate amount of time before sanding it. Then, wipe it off again with a paint prep pad to remove any dust residue.
Now you can lay down your color coat. You may want to test the color-match on an inconspicuous area of your vehicle before you spray it onto your vehicle.
Use short and even strokes by holding the nozzle for 10 seconds at a time and passing the can about 8 inches away from the surface to layer on the color.
You then let the first coat dry for about 20 – 30 minutes and add a second coat, and then a third if you’d like to ensure that the primer is not bleeding through.
Taking time to allow the paint to dry between coats will help reduce the instances of orange peel.
Finally, spray on 3 saturated coats of clear coat paint until you see a good luster and gloss. Wait at least 3 days before you wash it and several weeks or more before waxing. You have to let the paint dry out.
Aerosol spray paint is different from professional car paint because it lacks a hardener and will remain very soft until it dries out and cures.
Heavier Rust Removal
If you are fixing rust that has consumed large areas and you have scaling and what not, you will need to use a rotary tool and sanding disk to strip it away.
You can then use a rust converter to seal, chemically alter, and neutralize any lingering rust molecules before you seal and repaint the parts in the same manner described above.
You may also have to add a layer of fiberglass resin filler to smooth out the parts before painting. This is a relatively simple process that is not much different than working with sandable primer. Except, you will need to combine the two parts of the filler and apply it quickly before it sets.
Welding
There are times where the rust damage on a vehicle will be too severe to correct by simply sanding the surface down. In these cases, you may need to acquire new floor pans or fenders to replace the parts altogether.
Most of these components are spot-welded into place on older vehicles and can be removed by looking for the spots where they are anchored and breaking the welds with heat or other methods.
Nevertheless, you should consult a professional at a body shop to carry out this work unless you’ve welded professionally before.
Welding is a hard skill to learn without professional training and can be hazardous to your health if you are exposed to toxic fumes or UV-radiation.
Rust Prevention
Investing in hydrophobic paint protection film, applying silicone sealants to exhaust parts and the underbody, or even having your vehicle sprayed with a hydrophobic oil-based undercoating before the winter season can help to reduce automotive oxidation.
Although undercoatings like asphalt can offer better protection against rocks being kicked up and damaging the metal, they can also trap moisture underneath them and, therefore, should be avoided.
Having the undercarriage of your car washed regularly to remove build-up is also an effective method of reducing wintertime corrosion.
