You may never look at your vehicle’s undercarriage, but if you do you’ll probably spot some rust. Rust occurs naturally over time with the vehicle’s exposure to the elements, and in most cases, it’s nothing to worry about. Still, you may decide you want to repair the rust and return your car or truck to its former glory.
Repairing rust on a vehicle’s underbody may cost anywhere from a few hundred dollars to a few thousand. A small spot maybe $100 to $200, while extensive rust removal and repair work may be $1,500 to $4,000 or more. The cost depends on the extent of the rust damage and the labor to remove it.
How Much Does it Cost to Repair Underbody Rust?
Minor repairs for small areas may be pretty cheap, costing around $100 or so. In those cases, the work would only involve some light sanding and repainting or recoating the surface. However, those situations are probably not the ones that would have you take your car to the shop for repairs.
When rust damage is more extensive, it can be quite costly to repair. If the entire underside of your car or truck is covered, you could be looking at hundreds or thousands of dollars.
| Rust Damage Level | Cost Estimate |
| Minor damage, small spots | $100 – $250 |
| Moderate damage, multiple areas | $300 – $600 |
| Moderate damage, large areas | $500 – $800 |
| Extensive damage | $850 – $2,500 |
| Major damage, large areas | $1,500 – $5,000 |
There are different types of rust that impact vehicles differently and also impact the cost to repair the damage.
For example, surface rust is typically considered minor or moderate damage. This type of rust only impacts the top layer of metal and it’s normally just a cosmetic concern. Surface rust is extremely common and you’ll find it on pretty much every vehicle if you look hard enough.
Surface rust is the easiest to repair, so it’s normally the least expensive type of rust to deal with.
The next type is scale rust. This is deeper than surface rust and it can cause structural damage if left untreated. Over time, the scale rust will cause the metal to become weaker as it flakes and corrodes. This type of rust is more labor-intensive to repair, so you should budget more for the cost to fix scale rust.
The worst kind of rust to have on your underbody is penetrating rust. This is rust that has progressed beyond the surface and scale rust, and it occurs when the metal is fully rusted through causing holes and breakage. The metal is normally very brittle and not structurally sound.
Penetrating rust is very difficult (sometimes impossible) to repair, and it’s the most expensive kind to deal with. It can be an extremely labor-intensive process meaning that you’ll end up paying for many hours of bodywork to get the job done.
Can You Repair Underbody Rust?
Underbody (or undercarriage) rust can sometimes be repaired, but it may be an expensive process. Whether or not the damage is repairable depends on how extensive the rust is. A small amount can likely be removed with some sanding and touch-up paint, but large amounts of penetrating rust will be a bigger challenge.
In some cases, if the rust damage is too extensive, the entire vehicle frame may need to be replaced. Or, large sections might need to be cut away and replaced, which requires a lot of time and labor. Such repairs aren’t normally worth it for most cars or trucks.
However, if you decide to move forward with rust repair, the technician will start with sanding down the area until all the rust is removed and they hit clean metal. This also requires that they sand off any paint or coating in the area.
Then, they’ll add a special filler to the area to replace what they sanded away. If the metal is too thin or brittle, they may need to use a mesh material to cover it first.
Afterward, the technician will repaint the entire area so that it matches. For your underbody, they may apply a protective coating to help prevent more rust from developing.
How to Prevent Underbody Rust
Some rust underneath your vehicle is unavoidable and should be expected with normal wear and tear. Still, there are some steps you can take to minimize rust damage and keep your car or truck in tip-top shape.
Keep it dry
Of course, it would be impossible to keep your vehicle’s undercarriage completely dry, but you should avoid driving through large puddles whenever possible. Splashing water and other road contaminants onto your vehicle’s underbody is a big contributor to rust development.
Beware of salt
Rust is way more common in areas where they salt the roadways. So, if you live in the north or even if you live near the beach, you should plan to wash your car more frequently and clean the salt contamination from your underbody.
Visual inspections
It’s a good idea to look underneath your vehicle from time to time to check for rust damage. If you catch it early, rust is much easier to deal with versus waiting until it becomes a bigger problem.
Spot treatments on these small areas will prevent them from spreading.
Apply a protective coating
Most vehicles come with a protective coating on the underbody when they’re brand new. This coating wears off over time, leaving the metal exposed and vulnerable to rust damage.
You can have the coating reapplied to extend the protection for many years, especially if you live in an area where it’s wet, humid, or salty.
Things to Consider Before Repairing Underbody Rust
Repairing rust damage can be really expensive, so there are some factors you should think about before deciding to have it fixed.
The extent of Damage and Repair Cost
Depending on how extensive the rust damage is, the cost to repair it could be thousands. Before you commit to a very costly repair bill, be sure to get thorough estimates so you know what to expect.
Remember that repairing rust damage requires sanding and filling the visible rust and a pretty large area around it. So, take a close look at how much rust is visible and think about the true extent of the repair work you’ll need.
Still, if the damage is only surface rust, it may be a good idea to address it early so you can prevent further rust damage and more costly repairs.
How Much Your Vehicle is Worth
It may get to a point where the cost to fix the rust damage(unlike sun damage) isn’t worth it based on your car or truck’s value. If you plan to keep the vehicle for a long time or if it has some sentimental value to you, then it may be worth it to invest in the repairs.
On the other hand, if it’s an old beater truck you plan to get rid of in the next few years, you probably don’t want to dump a bunch of money into it for fixing rust damage.
Cosmetic Damage Vs. Functionality
In many cases, a little rust is purely a cosmetic concern. However, whether it’s just an eyesore or something that will impact your vehicle’s functionality depends on where the rust is located and how severe the damage is.
For example, rust on the frame is more concerning than some surface rust on the muffler. Depending on where the rust is located and whether it’s truly causing a problem is a huge consideration when it comes to whether or not you should repair the damage.
Anything that could impact the vehicle’s safety features or cause a hazard for the driver or passengers should be addressed right away.
How Much is Underbody Coating?
It normally costs between $150 and $500 to have a protective coating applied to your vehicle’s underbody.
Your price will ultimately depend on your specific vehicle’s size and the type of coating you choose. Some body shops offer options with extensive warranty coverage, which you should expect to cost more than those without warranty coverage.
Keep in mind that a protective coating will only prevent future rust damage. It won’t do anything for existing rust that’s already present.
So, if you invest in having the rust repaired, it’s a good idea to apply an undercoating to help prevent the rust from coming back and causing problems all over again.
The Bottom Line
Repairing rust damage can be very costly. It’s probably only worth it in cases of surface rust or small areas that can be repaired for a few hundred dollars. Extensive penetrating rust will probably cost more to fix than you’ll want to spend unless you plan to keep the vehicle for a long time.
Prevention is key when it comes to underbody rust. Try to keep contaminants off your vehicle’s metal surfaces and consider a protective coating to help keep rust at bay, especially if you live in areas where rust is more prevalent.