First, moisture and carbon dioxide in the air mix to create a weak acid that starts to dissolve the iron. Think about how easy it is to crumble a flake of rust between your fingers, and then imagine that stuff trying to protect you and your loved ones during a car crash.
A stray piece of gravel or a minor fender bender is all it takes to chip a car ’s paint, and any iron in the body panels will start to rust as soon as air and water reach the metal beneath it. That means rust spots can be fairly common on used vehicles, particularly if they’ve been driven in a northern U.S. state that uses chemicals and salt to device winter roads.
But if the rusting process goes on too long, it can eat right through the metal, causing holes and allowing body panels to fall to pieces. This is where problems go from cosmetic to dangerous, because modern cars and SUVs rely on these body panels for their structural integrity.
The most serious problems occur when rust gets beneath the car ’s surface and within its underlying components. Rust -free body panels boost a vehicle’s structural integrity, but the parts doing the heavy lifting lie under the car ’s skin.
Unfortunately, this area of a vehicle is often susceptible to rust -causing chemicals and water, which can accumulate there when a car drives down wet or icy roads. Most customers should avoid used vehicles that show strong signs of structural rust.
CARFAX also recommends getting an expert inspection that includes putting the vehicle up on a lift, to give your mechanic a better view of under body components. You can apply touch-up paint to stone chips, small scratches, and other minor nicks and dings, but truly repairing rust can take several steps, a variety of tools and materials, and quite a bit of skill.
Depending on the size and severity of the rust, blending the repaired area with the surrounding paint may require wet sanding or buffing the surface. Dirt can retain and trap moisture, and road salt, bird droppings, and other corrosive materials will eat away at paint if they’re left unattended on metal surfaces for long periods.
Waxing it on a regular basis (twice or more each year) will add a protective surface to the paint and clear coat. Wash and wax more frequently if you live near an ocean or in an area where highway crews spread salt on the roads to melt snow and ice during the winter.
Also, frequently check the fender liners and other areas under the hood, along the sides of the engine bay, for any standing water. Check the trunk or cargo area to make sure water isn’t seeping past the seals.
Stone chips and other nicks and dings that are left unrepaired can develop into rust spots over time, so it pays to buy some matching touch-paint to cover those imperfections. Learning how to handle chassis rust and prevent it from happening again can add years of life to your automobile.
Corrosion is a daily hazard for millions of American drivers, but it doesn’t have to be a death sentence for your car or truck. The underside of your car is at a higher risk of corrosion, because it’s more likely to stay wet after you drive in a rainstorm, as the sun can’t reach it to dry it out.
Over time, as these areas stay almost constantly wet, that trapped water will wreak havoc on the metal of your vehicle. Salt speeds up the electrolytic reaction that occurs between iron and oxygen in the presence of water, so a wet and salty undercarriage during the winter months is at an even higher risk of rusting out.
You can help keep things free of corrosion by adding your own light covering of oil or undercoating, which will cling to the metal and repel water. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.
I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry. I spotted some rust on the underside of the car between the back wheels.
By the time the inspection was completed (and failed), I had a hole in my muffler system along with about $2,500 worth of rust related repairs for a $1000 vehicle. However, to check you're going to have to do the squeeze test between fingers and thumb on the thicker structural sections, then if you still can't determine how severe or not the rust is. It's time to get an old screwdriver out and tap (with the handle part) on the rustiest bits.
If the material is corroded right through holes will likely appear, this is not good especially in the structural sections, if this is the case then you may like to walk away from this one as welding will be required. If however it is just surface rust then a scrap off and clean up followed by an application of under body protection will suffice and your good to go.
The seller should have no issues at all with you taping on the structural parts of the body to check its integrity. In some parts of the world where lots of salt is used in the winter, this is not unusual rust.
Occasionally called “cosmetic rust,” there’s no doubt that it’s ugly but it’s also fairly localized. Spots like this usually happen after a rock-chip penetrates the paint causing the exposed metal to react with water, air and other contaminants.
“This type of corrosion does not usually cause concern as it can be easily repaired with proper body preparation and re-painting,” reassures the expert at Known. Usually, these small surface spots can be fixed quite easily and some people even manage to do it from the comfort of their own garage.
“Similarly, light surface rust on the underside of a vehicle also is cosmetic and is not concerning,” Shuttle worth said. If you didn’t realize a rock-chip had affected your paint-job and left your car dirty for a while, then it’s feasible this kind of corrosion can happen.
Also, if you’re buying a car with an issue like this, likely it wouldn’t be able to pass a safety test without being patched up first. Bad enough frame rust can cause parts to snap off or crack, which will really compromise the safety of you, your passengers and other motorists.
“This will help to protect your investment and will give you peace of mind that you have made a smart purchase.” And for those who deal with arctic climates or live in areas that frequently use road salt or mag chloride, it can be a lifesaver to protect the undercarriage of your daily driver.
If you live in the Northern USA or in coastal regions like Houston, Louisiana, and other cities, it’s quite possible you’ve been introduced to the term undercoating. The undercoating is sprayed on the chassis and is marketed and advertised to customers as a rust protectant that also helps reduce road noise.
Rustproofing is a process that involves the application of protective waxes or other coatings on other areas that are made of corrosion-prone materials on the outside of the vehicle. To be honest, most cars, trucks, and SUVs made today have some rust protection ingredients mixed into the materials.
Plus, more and more daily drivers are using materials like Aluminum that naturally resist the development of rust. The coating itself is a tar-like substance that ‘sticks’ to the undercarriage components and acts as a barrier to resist salt, moisture, oxygen, and other items that lead to corrosion.
It circulates a weak electrical current through the materials, which reduces the potential of corrosion. Drip oil spray is an incredibly messy, but very effective method of protecting the undercarriage.
When it’s sprayed, it fills all the nooks and crannies of the chassis, providing an exceptional layer of protection. In fact, it’ll continue to drip for a minimum of 48 hours in most cases, and not fully cure for up to a week.
When metal corrodes, electrolytes supply the fuel (or oxygen in this case) to the anode. Most undercoating products last for multiple years, with some offering a ‘lifetime’ warranty against corrosion.
The biggest advantage of undercoating products is the protection against corrosion for longer periods of time. An extra layer of insulation is always a good way to reduce noise from penetrating materials.
Whether it’s a home or your car, the more ‘padding’ between you and the source of the noise, the quieter things will be naturally. However, it can get messy, cause your vehicle to be out of service for a few days while it cures, and is usually more time-excessive vs the amount of money to have a pro take care of it for you.
The first thing you need to do is fully debris the undercarriage or all areas you intend on treating with the spray. Generally, spray, let it soak for a few minutes, then remove with shop rags or microfiber towels you don’t mind trashing.
It’s a good idea to use a mild grinding pad and take a progressive approach to removal. Sanding : After all the crap is off the surface, use a 200 to 400 grit sandpaper to remove scratches and other small contaminants.
The best type of primers is those with high zinc levels, as this really helps to reduce that whole corrosion process if the surface layer is penetrated. When you’re finished with the process, the undercarriage should be well protected from saltwater, mag chloride, road grime, and other contaminants that cause oxidation and corrosion to occur.
Having a car treated with an undercoating is a very smart way to reduce the build-up of corrosion and extend the lifespan of your vehicle. A ceramic coating is a great way to extend life, protect the shine, and keep the surface of your car cleaner, for longer periods.
Investing in a high-quality DIY ceramic coating like Armor Shield IX is a great way to ensure corrosion doesn’t turn your ride into a rust -bucket. And the best part, we treat our customers like family, so if you have any questions or just looking to chat about cars, we're only an email or call away.