Problematic rust stains on a car generally expand over time as the metal on the underside is exposed to moisture and air, causing it to rust or corrode. Whether you plan to keep or sell your car, it will look cleaner (and cost more) without the rust, so feel free to remove it immediately. Remove rust stains from your car and apply a fresh coat of paint as soon as possible to stop rust damage before the stain spreads.
Method 1 of 2: Buffing and repainting the rusted areas
Step 1. Take basic security measures
This method involves using a sander and an emery board, two powerful power tools that can spread fine rust and paint dust into the air. To avoid damage and protect yourself from these airborne particles, be sure to wear gloves, safety glasses, and "especially" a dust mask to prevent rust and paint chips from entering your lungs.
When doing heavy tasks, consider wearing a respirator instead of a simple dust mask
Step 2. Cover the areas you want to protect from dust
As mentioned above, this job spreads paint and rust particles into the air. If you're not careful, these particles can settle on the car and give it a "dirty" appearance that can be difficult to clean. To avoid this, cover the parts of the car that you will not be working on with masking tape and masking paper. Use a duct-taped tarp under the car to define your work area and protect the floor.
Covering the car with masking tape and masking paper is a delicate art. Don't use newspapers because spray paint can seep and leave unsightly stains. Instead, use real masking paper because it is less porous and prevents paint from seeping through. Also, be sure to cover each edge of the masking paper with masking tape. Don't just use a few small pieces of tape to secure the paper in place, as paint will likely seep under any loose edges
Step 3. Cover the car with masking tape and masking paper along the lines of the existing panels
In general, you shouldn't put masking tape or masking paper in the middle of a panel or it will leave visible lines where new paint ends and old paint begins. If that happens, you won't be able to remove those lines by buffing them or applying clear coats of paint. Therefore, avoid this inconvenience by covering the car correctly, stopping on the lines of the panels around the rusted areas and avoiding going beyond the inside.
If you have experience painting cars, you can also stop applying the masking tape and masking paper a few panels behind the rusted area. If you know how to mix the paint gradually, which is done while spraying the paint, you can use this tactic to do it so that there isn't a drastic color difference between one panel and the next
Step 4. Remove the paint around the rust with a double action (DA) sander
A dual action sander provides control over your speed while removing paint. Start with 80 grit sandpaper and work your way up to 150 grit. Use the dual action sander with 80-150 grit sandpaper to remove primer and paint, as well as any light rust that has not coalesced. with metal. Also, you should level the surface between the painted surface and the unpainted area.
When you're done, put on some gloves and touch the surface with your fingers. The area should be smooth
Step 5. Replace the sander with a metal emery board
Use an emery board to remove thick deposits of rust and expose any marks. Use the grinder slowly and in the right way, otherwise you could seriously damage the car body. Once you're done grinding, apply a rust remover acid to remove any remaining microscopic rust particles.
- You'd better use phosphoric acid to do this job. You can buy it at most auto parts stores.
- If you want, you can use a hole-filling putty or auto body putty (such as Bondo's) to even out some dents and fill in the gap without paint. Finish applying the putty by hand sanding with 120-grit sandpaper to get a nice smooth metal surface. Read on to learn more about using putties.
Step 6. Prepare the area for primer application
Buy a special primer for painting on bare metal and spray paint in the color of your car. You can find both products at an auto supply store. Primers can vary, so follow the instructions that came with the primer or speak to an expert at the auto supply store for reliable information. Generally, you will need to do the following before applying the primer:
- Clean the area with white gasoline or paint thinner.
- Place newspapers over all surrounding areas within 3 feet (90 cm).
Step 7. Apply thin, even coats of primer
Spray three coats of primer and wait a few minutes between coats to let each one set. Don't apply too much primer to each coat to prevent dripping or smudging.
For most primers, you will need to let the fresh coat dry overnight (at least 12 hours)
Step 8. Sand with 400-grit wet sandpaper
This abrasive is specially made for sanding between coats of paint, smoothing the surface and removing the gloss so that the paint mixes properly. Keep a bucket of water on hand to rinse the sandpaper frequently and prevent it from rotting with paint. To finish, wash the painted area with a light mixture of soap and water.
Step 9. Spray a thin coat of paint
Apply thin coats of paint, letting each "sit" for a minute or two between applications so the paint doesn't run or sink. Apply as many coats of paint over the primer as necessary to achieve a nice color and finish.
Let the paint set for at least 24 hours before removing the tape. Be patient. If the paint feels sticky, you may need to wait longer
Step 10. Buff the edges of the new paint to blend in with the old paint
If necessary, apply a coat of clear paint that matches the finish of the rest of the car. Finally, let the paint harden for 48 hours.
Step 11. Wash and wax the car
Congratulations! Your car is rust free and ready for you to drive.
As a precaution, never apply wax to fresh paint within 30 days of painting the car because scrubbing or polishing the surface can remove the paint
Method 2 of 2: Using "putty patches"
Step 1. Grind the surface until "pure metal" appears
This method is a little different from the one described above. However, it works on the same basic principles, especially in rusty areas that have caused holes or marks. To start, remove all the rust with a metal grinder. You should grind down to reveal all the "pure steel" (no rust) around where the rusted area was, even if doing so leaves a hole.
- It is crucial that you get rid of all the rust. If you leave a small rust stain, over time that stain can corrode the surface underneath the car's paint and rust another area.
- Keep in mind that because you will be using an emery, the safety measures mentioned at the beginning of the article also apply for this method. That means wearing gloves, goggles, and especially a dust mask that protects your lungs from dust and paint particles.
Step 2. Cover the hole with a stainless putty
Then, you must apply a putty on the area where the rust was previously. You can buy commercial putties (like the one from the Bondo brand, mentioned above) at most auto supply stores at low prices. However, you may need to improvise if the holes are larger. In that case, you will need something smooth, very durable, stainless and that the paint can fix on to patch the hole. Place this object in the hole, apply a coat of commercial caulk, and let it dry.
Believe it or not, cut beer or soda cans work well for patching holes. The aluminum in these cans is naturally resistant to corrosion and many modern cans are covered with a thin protective layer. Another option is to use hard plastic sheeting
Step 3. Level the surface with sandpaper
Use sandpaper to create a smooth, even surface between the new "patch" and the car body. This can be a long and tedious process. As you sand, you will probably find that you need to add additional caulk and allow it to dry regularly as you remove the existing caulk. However, the process can be described in this way: putty, polish, putty, polish, putty, polish …, etc.
- Start sanding with a coarse (low-grit) sandpaper to smooth out any bumps, gradually work your way to a medium sandpaper and finally to a fine (high-grit) sandpaper to achieve a perfectly smooth finish.
- It is recommended that for this process you sand by hand, slowly and constantly since mechanical grinders can remove patches.
Step 4. Place masking tape and masking paper around the work area
Then, you should apply a fresh coat on the rusted area that you have repaired. Prepare the surface by placing masking tape and masking paper over most of the car to protect it from primer and flying particles. Don't forget to cover the windows and tires as well.
Line up the edges covered with the masking tape and masking paper with the seams on the car body to hide any minor differences between the new and old paint (unless you are experienced enough to achieve a smooth blend)
Step 5. Apply primer and then paint
Apply a few thin coats of primer and wait a minute or two for each coat to adhere before applying another over the first. Let the primer dry overnight. Then, after about 12 hours, use 400-grit water-based sandpaper to sand the coat so that the paint will adhere properly. When you're ready, apply paint over the coat using the same strategy you used with the primer: spray a thin coat at a time and allow it to dry.
- As with the previous method, you can buff the edges of the paint or cover it with a clear coat to make that section match the finish of the rest of the car.
- Obviously, it is important to choose a paint that matches the current finish of the car. There is a specific color code for each vehicle that you can find on a sticker located somewhere on the vehicle. You need this information to match the color. Most salespeople at auto paint stores will be happy to help you. However, keep in mind that paint on old cars can gradually fade over time.
- Oxide converters are an alternative to lengthy procedures. These are primers designed to be applied directly to the rusted surface. Unlike scratching, priming, and painting, you don't have to remove the surface until the metal appears. The oxide converter has two main components: a tannin-based polymer and an organic polymer. The organic polymer provides a protective primer layer. Tannin reacts with iron oxide, converting it to tannate iron, a stable blue or black corrosive product. You can buy a can of rust converter for $ 3 at a mall.
- If the car has a very rusty area that covers much of the bodywork, you can ask a professional to take over the job.
- A sprayless bottle rust converter is great for small chips, even if they haven't started to rust yet. Pour some rust converter into a cardboard cup. That portion of the converter quickly breaks down when contaminated with bits of rust and you must discard the excess. Position it towards the edges of the painting in good condition using a toothpick. Before using the car, wait for several hours for the converter to finish working and drying. You can drive it once the surface is dry enough not to run. The converter leaves a rustic black coating that looks like a tar stain and is generally not visible through an intermediate, dark or metallic color. Touch-up paint will adhere to the converter.
- If the rusted areas are on or around the fender, it may be helpful to lift the car carefully using a wedge behind one of the wheels. Remove the wheel and unscrew the plastic that protects it. Doing so will allow you to hit any dents from the inside and have more room to grind and paint.
- Propellants have explosive properties, so do not create any sparks or flames, including lighting cigarettes, near the work area during the entire rust removal process.
- Wear gloves, safety glasses, and a dust mask to prevent rust and paint dust from causing irritation or damage.
- If you are using phosphoric acid, BE SURE TO READ AND FOLLOW the directions on the product packaging.