Why Brake Discs Rust and What It Means


Steel was first developed in around 300 B.C. in China and made its way to America by the late 1800s. With cars arriving shortly after, steel has been and still is the primary material used to make brake discs, rotors, calipers, and even brake pads. Steel is a fantastic material that humans have utilized since nearly the dawn of civilization, but it’s not without weaknesses as you can gather from its tendency to rust.

Why do brake discs rust, and what does it mean? Rust is caused by moisture penetrating your brakes over time, but with regular driving, this is not usually a concern. Surface rust will be cleaned off by contact with the brake pads during frequent driving. However, if you don’t drive your car often or take long breaks, rust can sit too long, causing pitting in the rotor and requiring costly replacements.

You don’t want to risk damaging your brakes and endangering your safety as well as other drivers’ safety. This article will cover everything you need to know about brake discs rusting, what it means, how to remove it, and long-term rust prevention.

Why Do Brake Discs Rust?

Steel is a material known for being durable and heat-resilient. This is why it has maintained its solidified position as one of the best materials you can utilize in vehicle construction.

However, water is the enemy of steel. Moisture from rain, condensation, humidity, and other sources outside of your control will slowly but surely cause corrosion. Furthermore, if you live in an area where salt is used on the roads for ice, this can cause corrosion to occur at an even more rapid rate.

It won’t happen overnight or even quickly, and you don’t need to be alarmed by a small amount of rust. This is perfectly normal and is cleaned off of your brakes by the brake pads with regular use of your car and consistent driving.

However, an issue arises when you have long durations between each drive, and the rust is left to sit there and build up.

If you take a long break from driving, such as 6-12 months off from driving your car, rust can sit too long, causing pitting in the rotor. This is a significantly worse problem because your rotor might be corroding and slowly losing its integrity. This often requires turning or a full-blown replacement.

Another factor that could be playing a part in your rust issue is that your brake pads must match the size of your brakes and rotor or the necessary contact with the brake pads that brushes off the rust build-ups will not occur.

As AMPM Automotive Repair describes it, “Rust on the brake rotor can cause pitting. The surface of the rotor should be smooth so it can have full contact with the brake pads. Brake pads must be the exact size to perfectly match the rotor. The more contact the brake pad has with the rotor, the more braking power your vehicle will have.

How to Remove Rust from Brake Discs

It is very easy to remove rust from your brake discs, but if the problem is more severe, you will need to take your vehicle into your local automotive dealer or mechanic for a replacement.

The steps to remove rust from your brake discs are as follows:

  1. Drive your car as usual at around 10-15 mph and then firmly apply the brakes. Press strongly but not rapidly to where you will jolt forward. It takes a harder brake to make firm contact between the brake pads and brake discs. It is best to do this in a parking lot instead of on the road.
  2. If this is not sufficient or you want to polish your brake discs quarterly to care for your car more, you can wipe them with a cleaning product especially made for this that will evaporate quickly, such as:
  3. CRC 05089 Brake Parts Cleaner
  4. Single Unit Disc Brake Quiet for Squeaky Brakes
  5. Spin Power Disc Brake Cleaner

Warning: Do not use oils on your brakes because this will lubricate your brakes too much, and you won’t be able to brake correctly or safely.

  • If rust is still apparent, you can use a coarse scrubbing tool like a wire brush, sponge, or steel wool. You can try a concentrated product but always mix them with water to dilute them slightly.

Some cleaners require you to take the entire rotor and discs off to submerge them in water, do not purchase these if you’re uncertain of how to take apart your vehicle and put it back together safely. It’s not worth risking an accident, so purchase cleaning products according to your ability to safely use them.

To reiterate, a bit of rust is normal and will not damage your car or impact your driving abilities. However, over time pitting can occur, and it might simply be time for a replacement (around 50,000 miles). 

If the rusting or squeaky brakes seem severe or due for an adjustment, take your vehicle in to a professional for an inspection.

Is Rust on Your Brake Discs Dangerous?

It is very easy for rust to build-up along with brakes not only because they are made from steel but more-so because of the combination of steel and the moisture-retaining, dark, and humid location of your car’s brakes.

Over time, without proper maintenance, regular driving, and properly-fitting brake pads – yes, it can become dangerous. However, most of the time, regular driving prevents the rusting from reaching the point of being hazardous.

Typically, you will replace the brakes before they can become a danger because of rust.

Replacement Schedule to Follow

The replacement schedule you should follow for you brake system is:

  • Brake pads will need to be replaced every 50,000 miles on average, (25,000 miles if in a colder climate with salt on the roads, rough conditions, or if the driver brakes hard which wears down your brake pads faster).
  • Brake discs should be replaced at the same time as the brake pads.
  • Brake rotors should last nearly three times as long (between 135,000 – 170,000 miles), but it will depend on how well you maintain it, climate, road conditions, and how hard you brake).

If you do not properly maintain your car or take it into a body shop once the rust begins to worsen, the risks you face are:

  • You will start to lose power over your brakes.
  • You will not be able to prevent wheel spin-outs in bad situations, especially on ice or slick roads.
  • It will weaken your rotor.
  • It will make things noisy as you maneuver.
  • It will wear down your brake pads.
  • You are risking your safety as well as other drivers’ safety.

Again, it takes a variety of factors to cause brake discs to rust excessively, and you will have plenty of warning signs to fix your brakes before they become dangerous.

In Conclusion

Some final tips to get the most life out of your brake parts are:

  • Drive your car regularly.
  • Don’t brake too hard but don’t brake too softly either; always brake firm and steady.
  • You can also take your brake parts out of your vehicle, wipe down any residue, and then spray them with a protective paint coat such as Caliper Rust-Oleum Specialty Rust Preventative

With regular maintenance, expectations, and turning and brake flushes, your brakes will run smoothly and make you feel safe.  If you have any questions or are concerned about a worsening rust issue, take your vehicle into your local mechanic, body shop, or dealership if it is still under warranty.

Arwood

I'm Arwood, but the grandkids call me Big Papa. After retiring from teaching automotive classes for 30+ years I decided to create a blog about all the questions I used to get about brakes!

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