The Proper Way To Fix Major Rust on a Car
You'll need welding experience.
Time Needed: 1 weekend to 1 week, Difficulty: Moderate to Professional, Cost:
WARNING: The real way to fix a large rust spot is to replace the area with new metal and weld it in. Welding is a difficult skill that requires specific equipment, hours of practice, and a lot of know-how. You should only attempt to make a welding repair if you have the experience, knowledge, proper tools, and proper workspace.
Although brand-new cars offer the trendiest designs and the most advanced new technology, the editors at Car Bibles are big believers in used vehicles, restoration, and dedication to maintaining a vehicle for the length of its life. That inevitably means running into and dealing with rust. Bleh.
Dealing with small rust spots can be fairly simple, but an oxidizing ‘92 Acura Integra GS-R from Wisconsin calls for the big guns. Major rust repair requires metalwork and welding, both of which can get quite tricky, so we want to repeat that this type of DIY how-to is for advanced wrenchers who know how to weld.
By repairing your rust, you’re not only fixing the aesthetic, but you’re also always rebuilding the car’s structural integrity, so it is an absolute necessity to do the work the right way. Below, we guide you through the basic steps of how the repair will play out.
The Safety Brief
Tackling a rust repair and welding in sheet metal can both be dangerous jobs in the shop. Absolutely do not do this without a welding helmet, welding gloves, safety glasses, mechanic gloves, and a respirator. It’s also not a bad idea to wear protective pants and long-sleeve shirts when welding.
The Tools & Parts You Need
At the minimum, you will need these tools and parts to complete the job.
- MIG welder
- Nibbler or grinder air tool for cutting out metal
- Air sander
- Sanding block
- Sandpaper discs and sheets
- Automotive masking tape
- Hammer and dolly
- Clamps and/or Vise-Grips
- Scribe tool
The Job: How To Fix Major Rust on a Car
Take it one step at a time.
- Knock off and remove any loose pieces of rust and metal.
- Go over the rust spot with a wet vac to clean up the area.
- Identify how far the rust goes. Knocking and poking on the metal will help.
- Once you know the shape of the rust spot, use a grinder to remove the surface around the rust until you get to bare metal. Stay as flat as possible as not to remove much of the metal.
- Identify the area you want to remove. Try to keep as much of the original metal as possible, but also be aware of the need to create a perfectly matched replacement piece.
- Use a scribe and a ruler to create the lines you want to cut.
- Use a grinder, nibbler, or other power tools to cut out the rusted area.
- Grind off any abnormalities or miscuts.
Creating the New Metal Panel
- Using a piece of cardboard, trace the shape of the cut hole.
- Cut the cardboard into the correct shape.
- Using a scribe, trace the cardboard shape onto a new piece of metal.
- Cut out the new piece of metal.
- Clean up the edges, again being cognizant not to remove too much of the metal.
- If necessary, bend the metal to the correct shape of the panel.
- Make sure the new piece is flush with the hole it goes into.
Although different situations require different types of welding, we are referencing MIG welding in this case. Again, only do this if you have experience with welding, and don’t forget the protective gear!
Cleanup and Finishing
- Grind or sand down the welds. Be very careful not to cut too much into the metal panels.
- Smooth out the edges and metal until it’s flush.
- Once the weld is clean and smooth, it’s time for primer and paint.
Congrats, there’s no longer a hole in your car!
The Car Bibles Questionnaire
Car Bibles answers all your burning questions!
Q. I Can’t Weld, What About Fiberglass?
A. If you’re cool with patchwork, then yes, fiberglass is fine, aesthetically speaking. However, the only way to do the job 100 percent correctly is to weld in a new piece of metal for strength.
Q. What Can You Spray On Rust To Stop It?
A. Rust converters such as Rust-Oleum’s Rust Reformer can help with that. As always, though, it’s best to address rust issues right away.
Q. What Can You Use To Prevent Rust?
A. Undercoating is a great way to protect your car, but there are also a variety of other types of rust prevention sprays available. As well as protective films that go over your car’s sheet metal.
Q. How Much Does It Cost To Fix Rust on a Car?
A. If it’s a major rust repair, you’re going to be spending lots of money either way. There’s no set price, but you’re looking at between a couple of hundred dollars to several thousand dollars depending on how extensive the rust is.
If you want to repair it yourself, you’ll have to buy a welder, which can cost a few hundred dollars, and that’s just the start of the parts you need. If you take it into a shop, rust repair can be a laborious job that takes hours to complete, so the labor charges rack up into the hundreds very easily.
Q. How Do You Remove Surface Rust?
A. Our guide to the best rust removers should help.
Video Tutorial on How To Fix Major Rust on Car
The Tools To Buy
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