How Long Does It Take for Rust to Form on a Car? (Stages of Rust)

Rust is a common problem that long affected the automotive industry. It occurs when metal is exposed to oxygen and moisture, causing it to break down and form a reddish-brown substance. Rust can quickly spread and weaken the metal, leaving unsightly marks and eventually causing structural damage.

Rust takes four to five days to form on a car after the paint has been damaged. When oxygen and water come in contact with the metal, they cause a chemical reaction that creates iron oxide. Certain environmental factors, such as salt water and acid rain, accelerate the rusting process.

While it may seem like rust suddenly appears, it actually goes through a long process before it becomes visible. Understanding how rust forms can help you identify the problem early on and take steps to prevent it from spreading. Read on to learn more about the stages of rust and how long it takes for each one to form.

Stages of rust on car.

How Rust Forms on a Car

Rust forms on a car after the paint has been scratched or damaged, exposing the metal beneath. This can happen from something as small as a rock hitting the car’s surface to bigger problems like hail damage or a car accident.

Car bodies are made of steel, an alloy of iron, and carbon. When iron is exposed to oxygen and water, it undergoes a chemical reaction known as oxidation. This process creates iron oxide, which is the substance we know as rust.

4Fe + 3O2 +2xH2O → 2Fe2O3.xH2O

If not addressed on time, rust can quickly spread and cause severe damage to the metal. In extreme cases, it can cause the metal to break down completely, destroying the car’s structural integrity.

The environment also plays a big role in how fast rust forms. Factors like salt water, high humidity, and acid rain can speed up the process. Cars in the coastal regions are particularly susceptible to rust due to the high levels of salt in the air.

Stages of Rust on Car

Like most things in life, rust doesn’t happen overnight. There is a process of decay that it goes through before it becomes visible. From its initial stages of oxidation to full-blown corrosion, rust can cause a lot of damage if left unchecked.

Stage 1: Surface Rust

Surface rust is precisely what it sounds like, rust that forms on the surface of the metal. This is the earliest stage of rust and affects the top layer of the metal. A crack or scratch in the paint will expose the underlying metal to oxygen and water, causing it to oxidize.

At this stage, the rust will only form on the exposed surface and will not have penetrated the metal beneath. Surface rust is not as serious as other forms of rust but should be addressed nonetheless. If left unchecked, it can spread and cause further damage to the car.

Stage 2: Scale Rust

Failure to address surface rust can lead to scale rust, a more severe form of corrosion. Scale rust is characterized by bubbles forming on the car’s paint. Since iron oxide molecules are bigger than iron molecules, they get trapped under the paint and cause it to bubble up. This expansion causes flaking, exposing fresh metal to the elements, and corrosion.

The salt in road salt accelerates the formation of scale rust and can cause it to form within days of the initial oxidation. It’s important to wash your car regularly during winter to remove any road salt that may have accumulated on the surface.

Correcting scale rust is a bit more complicated since the corrosion has already penetrated the paint. You will need to remove the affected area and apply a fresh coat of paint. In some cases, the damage may be too severe, and the car must be repainted entirely.

Stage 3: Penetrating Rust

After prolonged exposure to the elements, scale rust will eventually penetrate the metal beneath the paint and cause deeper corrosion. This results in penetrating rust which converts the metal frame to brittle iron oxide, causing holes form.

Penetrating rust compromises the car’s structural integrity and can cause serious safety issues. From weakened floorboards and suspension to collapsing roofs, this form of corrosion can quickly turn your car into a death trap. Regular inspection underneath the car’s body can help catch penetrating rust early on.

Treating penetrating rust is a complex and costly process that often requires the help of a professional. You will need to replace the affected parts or weld patch panels over the holes. Sometimes, the car may be too far gone and need to be scrapped entirely. If the car’s frame is compromised, driving it is not worth the risk.

Causes of Car Rust

As every car owner’s worst nightmare, rust can wreak havoc on your car if left unchecked. From unsightly brown patches to compromised safety, rust can cause much damage. But what causes this destructive force? Let’s look at some of the most common reasons why cars rust.

Weather Conditions

One of the most common causes of car rust is exposure to the elements. Oxygen and water are the two main culprits behind corrosion. Regular exposure to rain, snow, and sleet can cause water to seep into cracks and crevices on the car’s surface. This moisture then accelerates the oxidation process, causing rust to form.

Salt found in the surrounding air is another weather-related factor that can cause rust. Saltwater is highly effective at carrying electrons, which allows it to accelerate the corrosion process. That’s why cars in coastal areas are more susceptible to rust than in those inland areas.

Additionally, the road salt used to melt ice and snow in the winter can also be corrosive. The salt can splash up and cover your car when you drive over salted roads. If not removed promptly, it can cause rust to form, especially on the undercarriage.

Poor Maintenance

Proper maintenance is essential in keeping your car in tip-top shape and preventing rust. Allowing your vehicle to sit for long periods without washing it can increase its susceptibility to corrosion. Over time, dirt, grime, and other debris can build up on the surface and provide a perfect environment for rust to form.

Regularly washing your car and keeping it clean is one of the best ways to prevent rust. Washing removes dirt, debris, and salt which can accelerate corrosion. Waxing your car is also an excellent way to create a barrier against the elements and prevent rust from forming.


As your car ages, it becomes more susceptible to rust. The paint and other protective coatings on your car start to degrade over time, leaving the metal beneath more exposed to the elements. When water and oxygen come into contact with the metal, they cause oxidation and rust to form.

Older cars are also more likely to have cracks and holes in their surface. These provide the perfect entry point for water and oxygen to cause corrosion. That’s why it’s important to regularly inspect your car for any signs of rust and have it repaired as soon as possible.

Driving Style

While it may seem like an unlikely cause, your driving style can contribute to car rust. If you regularly drive on unpaved roads or off-road, you subject your car to damage and increased exposure to the elements. The dirt, rocks, and debris can chip away at your car’s paint, leaving the metal beneath more vulnerable to corrosion.

Poor Storage Conditions

How well do you take care of your car when you’re not driving it? Do you cover it with a tarp or store it in a garage? The way you store your car can have a big impact on its susceptibility to rust.

Leaving your car outside exposed to the elements is one of the worst things you can do. Not only does it increase its exposure to water and oxygen, but it also subjects it to the damaging effects of UV rays. Over time, this can cause the paint and other protective coatings to degrade, leaving the metal beneath more vulnerable to corrosion.

The best way to prevent rust is to store your car in a cool, dry place. If you don’t have a garage, a quality car cover will protect your car from excess moisture and prevent rust from forming.

Signs of Rust on Car

Unfortunately, rust is an inevitable part of car ownership. No matter how well you take care of your car, there’s always a chance that rust will form. That’s why it’s crucial to recognize the signs of rust and take action to prevent it from spreading.

Rust Spots

An obvious sign of rust is the appearance of rust spots on your car’s surface. These spots are usually red or brown and have a flaky or powdery texture. Rust spots are typically small at first, but they can grow and spread quickly if not treated.

They can also form on your car’s underside and in hard-to-see places like the inside of the wheel wells. Regularly inspecting your vehicle for rust spots is the best way to catch them early and prevent them from spreading.

Paint Bubbles

As rust begins to form underneath your car’s paint, it can cause the paint to bubble and peel away. Iron oxide molecules are bigger than water molecules, so as they expand, they push the paint up and cause it to swell.

The bubbles appear as raised spots on your car’s surface and are usually accompanied by rust spots. Having a professional inspect your vehicle for paint bubbles is the best way to determine if rust is present and if so, how extensive the damage is.

Water Damage Under the Trunk’s Carpet

As rust corrodes your car’s metal, it can cause holes and cracks to form. These holes and cracks provide the perfect entry point for water and moisture to enter your vehicle. Pull back the carpet in your trunk and look for any signs of water damage.

You may notice brown rust spots, mold, or mildew. If you see any of these signs, it’s a good indication that rust is present, and you should have your car inspected by a professional to prevent further damage.

How to Prevent Rust on Car

While rust is an inevitable part of car ownership, you can take steps to prevent it from forming. These include:

Washing and Waxing Your Car Regularly

One of the best ways to prevent rust is to wash and wax your car regularly. This will help remove any dirt, debris, or salt that could be causing rust to form.

The wax seals off the car’s paint and creates a barrier that prevents water and oxygen from reaching the metal beneath. Additionally, waxing your vehicle prevents water bubbles from sticking to the paint, which can cause rust spots.

You may also like to read: Best Car Wash Soaps and Shampoos.

Inspecting for Rust Spots Regularly

Regular inspection is key to preventing rust. This helps you catch any rust spots early so you can take action to prevent them from spreading. Inspect your car’s surface regularly for red, brown, or orange spots.

You should also look for any paint bubbles, as these can indicate rust forming underneath the paint. If you find any rust spots, have your car inspected by a professional to determine the best course of action.

Applying Rust Proofing Products

Applying a rust protection product can also protect your car from rust. These products usually come in the form of a spray or gel that you can apply to your car’s surface. Rust protection products create a barrier that prevents rust from forming. Some products also have ingredients that help break down existing rust and prevent it from spreading.


When your car’s paint is damaged, rust generally will start forming within four to five days. If the damage is left untreated, rust can spread quickly and cause extensive damage to your car. To prevent rust from forming, it’s important to inspect your vehicle regularly for any signs of damage.

If you find any rust spots, have your car inspected by a professional to determine the best course of action. Applying a rust protection product can also help prevent rust from forming as it creates a barrier that prevents water and oxygen from reaching the metal beneath.



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