Vehicle Rust and Corrosion: Common Causes and Prevention

No matter what type of vehicle you drive, its body and frame are constantly fighting against the most common causes of rust. When bare metal comes into contact with oxygen and moisture, oxidation takes place and can result in rust if not treated. Rust and corrosion can be caused by several different environmental factors, and while there is no particular age when cars begin to rust, there are a few common reasons for corrosion. Even newer vehicles with rust-preventive materials and specialty coatings can succumb to rust under certain conditions. Wear and tear, climate, and road conditions are only a few of the most common reasons why your vehicle may fall victim to rust. Being aware of these conditions and performing appropriate maintenance is one of the best ways to prevent rust formation on your vehicle, and knowing which car parts and components are most likely to rust is essential when inspecting your vehicle for corrosion damage. Read on to learn more about common rust causes, rust prevention, rust and corrosion treatment, and more.


Common Rust Causes

Understanding what puts your vehicle at risk of rusting is the first step in preventing corrosion. Depending on the type of vehicle you drive and the driving conditions you experience day to day, the risk of experiencing these issues may vary. We’ve detailed a few of the most likely causes of rust on your vehicle below.

Vehicle driving on snow-covered road

Climate and Road Conditions

All types of weather conditions can be a contributing factor to vehicle rust. Climates with consistent precipitation or harsh elements, such as regular exposure to rain, snow, ice, hail, or sleet, can increase the chances of moisture oxidizing the metal parts of your vehicle. If you often drive your vehicle in colder climates, you may also experience ice and roads that are treated using salt. Over time, the chemicals in road salt can begin breaking down your car's protective coatings and finishes, and rust can form. UV rays from sun exposure can also cause the protective coat on your vehicle to begin to delaminate, exposing the paint and primer layers to the elements. This can also result in corrosion if it is not addressed and moisture is able to penetrate the car’s finish. If you often drive on unpaved or gravel roads, dirt, rocks, and road debris can cause chips that can also leave the bare metal exposed to harmful contaminants and increase the risk of rust formation. Learn how to prepare your vehicle for winter and summer to protect it from rust with our helpful articles.

Vehicle Age

While vehicles of any age can be affected by rust, some older vehicles have a greater risk than others. Over time and with use, all vehicles experience wear and tear. Whether from an accident or fender bender, or simply from being driven for years, your vehicle’s paint and protective coatings can begin to break down over time. These layers of clear coat, paint, and primer are designed to protect your vehicle from harsh elements and contaminants and are necessary to shield the metal body and frame of your car from corrosion. If these layers are damaged, scratched, or simply worn down from exposure to the sun or other elements, your vehicle is at a greater risk for rust formation. Some older vehicles were also designed with nonreactive and less protective coatings, leaving them more susceptible to rust over time. Cars manufactured before the 1990s were typically not engineered with any kind of effective undercarriage coatings to protect against road debris or salt, and are more likely to experience rust.
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Soapy sponge washing a vehicle

Maintenance Neglect

Neglecting your car's maintenance and service needs can also lead to rust and corrosion buildup. If you don’t regularly wash your car to remove any dirt or road debris or inspect for existing damage or rust, your vehicle may be at even greater risk of corrosion. Rust can also form under the hood and the undercarriage of your vehicle, so inspecting all of these hard-to-see areas when performing regular service checks or maintenance tasks is a great way to detect any rust, or potential causes of rust, before the damage is too extensive. Frequently parking or storing your vehicle outside also leaves your car at the mercy of the climate and weather conditions around it, so if possible, parking under some sort of shelter or in a garage can help keep your vehicle rust-free as long as possible.
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Common Rust Spots

While rust can form anywhere on your car, there are a few areas that are more susceptible to rust than others. In some cases, rust can form inside a body panel or part and work its way out, making it harder to recognize without a thorough inspection until it’s too late. When performing vehicle maintenance, it is a good idea to take a look at these parts and inspect for any signs of rust or corrosion, or take note of any scratches or damage that could result in rust or corrosion. A list of the most common rust spots for most vehicles has been prepared below.


  • Side Panels, Hood, and Roof – If you notice paint peeling or bubbling on your vehicle's doors, hood, or roof, rust could be the cause. In most cases, rust is only part of the problem. Oxidation can form if your vehicle’s paintwork is damaged, leaving your vehicle’s metal body susceptible to corrosion.
  • Wheel Wells – Contaminants and road debris can become stuck inside or damage the arched curves above your tire, and this can result in rust or corrosion if it is not addressed. This is most common in older vehicles without wheel well covers or liners.
  • Exhaust – Your vehicle’s exhaust system is consistently exposed to moisture from inside and outside of your vehicle, as well as contaminants and road debris such as mud, dirt, road salt, or dust. This can result in rust if the bottom of your vehicle is not cleaned and maintained regularly, especially in older vehicles. Moisture can also build up inside the exhaust system if the car is only driven for short periods of time, causing the exhaust pipe, muffler, and other parts to rust from the inside out.
  • Frame Rails and Rocker Panels – The frame rails and rocker panels on your vehicle are located underneath and on both sides of your car, and are often covered in snow, rain, ice, mud, dirt, or other climate-based contaminants. The frame may also have openings that can allow mud, moisture, and other contaminants to enter, and it can be difficult for them to escape. This can cause a buildup in the frame that may trap moisture and cause rust from the inside
  • Suspension – Due to its location, your vehicle’s suspension often comes in contact with moisture and road debris being kicked up by the tires. These contaminants can lead to oxidation and rust that can impact your vehicle’s suspension components if left untreated. Moderate surface rust on suspension components is common, but if the rust causes structural damage, the affected parts may need to be replaced.
  • Doors – Moisture can also enter the door through the window channel, and if the drain holes in the door are blocked, may build up inside the door and lead to corrosion.

Types of Vehicle Rust

There are many areas of your vehicle that are affected differently by rust. Depending on the area and type of rust, the extent of the rust damage and its effect on your vehicle may vary. Read on to learn about the different types of rust on your car.

Surface level rust on a vehicle

Surface Rust

Surface-level rust only affects the top layer of your car’s sheet metal, and typically appears in bumps, scratches, or nicks on your vehicle’s side panels, hood, or roof. Paint may also begin to bubble during this stage of rusting. Treating the damage and repairing any paint scratches promptly and correctly can usually stop the rust from spreading before it becomes a bigger problem.
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Scale rust on a vehicle

Scale Rust

If surface-level rust goes untreated, scale rust can begin to form and spread. Scratches and peeling car paint can allow contaminants and debris, such as road salt, to speed up the corrosion process. This puts the metal frame and panels of your vehicle at risk and poses a threat for more extensive damage to form. This may result in the need for body and automotive paintwork repairs.
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Penetrating rust on a vehicle

Penetrating Rust

When surface and scale rust are neglected or not repaired correctly, penetrating rust can set in, leaving holes in the metal. Penetrating rust is the most damaging type of rust on your vehicle, and in extreme cases, can even result in the need to replace entire car parts, panels, or components. Rust and corrosion at this level is the most costly to repair and will likely need to be serviced by an autobody shop or mechanic.
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How to Repair Rust

While extensive penetrating rust and corrosion damage may need to be repaired by a professional autobody shop, most surface-level and scale rust can be repaired by anyone with the right tools and supplies. If you find any rust spots or paint bubbling on your vehicle, you can likely stop it from spreading and repair the problem area before it becomes a more extensive repair job. Some paint scratches and chips are smaller in scale and easier to repair than others with the help of our paint scratch repair article. However, if the rust spots are too severe, your repair may be a bit more in-depth than repairing the original paint scratch or chip. Check out our other automotive paint and appearance articles for a detailed, step-by-step guide on applying touch-up paint to your vehicle. Below are the steps to diagnose and repair rust on your vehicle.


Step 1. Identify Spots of Surface and Scale Rust

Locating the problem and addressing it as soon as possible is the best way to prevent the rust from spreading any further on your vehicle. Surface rust is typically lighter in color and smaller in size, and may be the result of paint scratches, abrasions, or peeling. Scale rust is usually darker in color, more widespread, and deeper, typically having a notable texture. If you notice either surface or scale rust, it should be repaired immediately. If you find penetrating rust, the metal will need to be replaced completely.


Step 2. Identify the Paint Code For Your Vehicle

If you can repair the damage at home, you will need to apply a fresh coat of automotive primer, paint, and clear coat to the damaged area. To locate the correct paint code for your vehicle, search for the label on the inside of your driver-side door, or find the information in your owners manual. This code will ensure that your new paint matches your vehicle color perfectly, though if the paint has faded significantly with age, the fresh paint may not be an exact match.

Select O’Reilly Auto Parts offer professional paint matching and custom paint mixing for most vehicles. For more information about our automotive paint mixing services, visit our store services page.


Step 3. Prep the Area

Before applying your paint, wash and sand the affected area. Using 40-grit sandpaper, sand the rust until the area has a smooth finish. After sanding, it is important to wipe off any dust or debris from the area and wash it before applying primer and paint. It is also recommended to use automotive masking tape to tape off the area to avoid unnecessary sanding or paint overspray.


Step 4. Apply Rust-Neutralizing Primer or Rust Treatment

Before applying primer and paint, it is a good idea to add an extra layer of defense to help ensure the rust doesn’t return underneath the new coat of paint. Applying a rust-neutralizing primer or rust treatment before priming is a good way to prevent rust from forming. These solutions work by transforming the iron oxides that cause rust into a protective barrier, preventing further rust formation. This can also take the place of the primer and allows the metal to be painted over again with less risk of rust or corrosion forming under the paint.


Step 5. Primer, Base Paint, and Clear Coat

To properly repair the rust spot or damaged paint, you will need to apply a layer of primer, base paint, and a clear coat. Without the layer of primer and clear coat, the autobody paint may only last for a short period of time before environmental factors begin to break down the paint, resulting in the need for more repairs. Paint bonds to the primer, and the paint and clear coat are also chemically bonded, creating the strongest defense for the body of your vehicle. For more information on painting and priming a vehicle, visit our helpful article about how to apply touch-up paint. Reviewing and following manufacturer specifications for dry time, sanding, and more can also help ensure that your paint repair is done right and lasts as long as possible.


Prevent Rust On Your Vehicle with Products From O’Reilly Auto Parts

Taking care of your vehicle and maintaining its appearance is a great way to protect it from the effects of the environment, contaminants and pollutants, and wear and tear that can occur with use and over time. Completing regularly scheduled autobody maintenance checks and inspections is a great way to catch potential damage before it becomes less manageable. Knowing how to repair paint scratches, how to use touch-up paint, following routine vehicle checklists, and frequently washing your car are also great ways to reduce the effects of road debris, outdoor elements, and wear to keep your vehicle looking its best and as rust-free as possible. Find the car wash, paint repair, and detailing products you need at O’Reilly Auto Parts, and visit our How-To-Hub to find guides and resources to help you keep your car looking and running at its best.