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Exclusive X-Coat Rustproof treatment on all our Premium X-Coat and Black XD Rotors guaranteed to resist up to 1000hrs of salt and water exposure.

 

Most drivers that have left their cars outside in wet conditions for a week or more while not driving them in the interim have almost certainly heard that unpleasant sound of a simultaneous high-pitched squeal and low creak when they apply their brakes for the first time. This sound is a tell-tale sign of rusty rotors. Rust developing on brake rotors is a relatively common occurrence and almost all drivers have some degree of rust on their car’s rotors. When brake pads make contact with brake rotors, they do eventually clear the thin layer of rust on the contact areas so that they can continue to do their job. However, there are other deleterious effects of rusty brake rotors. This guide describes the problem of rust on brake rotors and gives advice for how to find brake rotors that do not rust. Using such rotors can help drivers put many more miles on them before they need to be replaced.

The Problem of Rust on Brake Rotors

Brake rotors are often made from cast iron, a metal that is susceptible to surface rust. This section details the problem of rust on brake rotors, covering causes for rust and pointing out what the negative consequences of rust developing on brake rotors are.

Causes for Rust on Brake Rotors

Rust develops on the rotors when they become wet and then sit for an extended period of time. It is easy and normal for rotors to get wet, as simply driving in the rain will cause this. It is also normal for a car to sit in a garage for a few days at a time. If a car sits with wet rotors, the rotors will begin to rust and that rust will build a little more every time that the car sits for a few days with wet rotors. Cars that are not parked in garages are especially susceptible to rusty rotors as the rotors are more often exposed to wet conditions. Drivers who live in areas that use salt on the roads in the winter will also find that their rotors rust extensively because the salt has strong corrosive properties.

Are There Negative Consequences of Rust on Brake Rotors?

As mentioned in the introduction, a car’s brake pads usually scrape surface rust on the brake rotors off where the two components make contact the first few times that the brakes are applied. The area of the rotors that made contact with the pads is the part of the rotors where it is most important for them to be rust-free since the friction this contact is what stops the rotors (and therefore the wheels) from turning, which allows the car to brake. Rusted rotors will therefore not be as effective the first few times that a car brakes, though they should operate fine thereafter. The pads and rotors will also cause an unpleasant sound if the contact area between the two has rust on it.

Rusted rotors can also present a problem when it is time to replace the rotors. Extensive corrosion can make them difficult to unmount, so those that do their own brake work will make their jobs easier if they have rotors that do not rust. Furthermore, it is best to keep the lip of the rotor free of rust as this can diminish the effect of pad contact as the rotors and pads wear down.

Finding Brake Rotors That Do Not Rust

One solution to preventing rust on brake rotors and the problems that it causes is to find brake rotors that do not rust. This section outlines this process, including determining which brake rotors do not rust and locating rust-proof brake rotors. It also presents a few other preventative measures that can help to defend brake rotors against rust.

Determining Which Brake Rotors Do Not Rust

The table below presents information on the various types of carbon rotors that do not rust, including a description of the rust-proof material and its pros and cons.

Material

Description

Pros

Cons

Zinc

Zinc is a plating that resists the oxidation that leads to rust.

They are inexpensive and protect the majority of the rotor.

They wear off immediately on brake pad contact areas.

X-Coat  (Electro-Coat)

X-Coat  is another plating that resists oxidation.

They are very effective against corrosion from salt.

There are environmental concerns over the toxicity of their material.

Composite

Composite rotors are made from rust-proof carbon-ceramic material instead from metal.

They are rust-proof and can last 100,000 miles under normal driving conditions.

They are initially VERY expensive, though their costs diminish over time due to durability but is only worth it on exotic cars.

Zinc and X-Coat are both platings or coatings, and they will come off rotors where the brake pads make contact within the first few times a driver applies the brakes. The remainder of the rotor’s surface area generally retains the coating for a few years, preventing rust from building up in spots where it is difficult to remove.

Locating Rust-Proof Brake Rotors

After deciding between zinc-plated, cadmium-plated or carbon composite brake rotors, the next step is to find a seller of the chosen rust-proof brake rotors. Many local automotive parts stores sell all three types of rust-proof brake rotors. These are good sources from which to buy rust-proof brake rotors because the employees of these shops can often provide expert advice about the different types of brake rotors that they sell and can set proper expectations for customers regarding the rust-resistance capabilities of the rotors.

There are also many online sellers of automotive parts that carry rust-proof brake rotors. A number of these sell them directly from wholesalers’ warehouses, offering reduced prices since the rust-proof rotors do not go through retailers before arriving in buyers’ hands. This can be an excellent way to save money on rust-proof brake rotors, but buyers may receive the same level of personal customer service that they would get in their local automotive parts store. However, online retailers are often available to answer customers’ questions and help ensure that they are buying the brake rotors that they want and need.

Other Preventative Measures

Buying brake rotors that manufacturers have rust-proofed during production is the most convenient way to prevent rusting on brake rotors, but there are a few other measures that drivers can take to thwart rusting from occurring. If drivers are handy, they can choose to buy their own zinc and X-Coat coatings and apply them to their rotors themselves. Drivers should make sure that they have the necessary equipment to do this, however, including using protection against toxic fumes. Tire covers can be helpful for cars that drivers usually park outside. These protect tires and wheels, including brake rotors, from the elements, which in turn limits corrosion. Lastly, those drivers living areas that have salted roads during the winter can wash the undercarriage of their cars frequently, especially after driving in the wake of a snowstorm. This will wash the salt off the rotors, preventing them from rusting.

Conclusion

Rusty brake rotors are not the end of the world. They are not even the end of the rotors. It is normal for brake rotors to rust and for brake pads to then remove the rust in the critical contact areas with the rotors as drivers brake their vehicles. Although rusty brake rotors are unlikely to cause a hazardous situation, having rust-proof rotors does possess a few benefits. The rotors can last longer than rotors that rust do, and they are easier to remove from vehicles than rusty rotors are. The three options for brake rotors that do not rust are zinc-plated rotors, cadmium-plated rotors, and carbon composite rotors. Each has its own costs and benefits, so drivers should weigh these before deciding where to buy these rotors. This guide has given a number of suggestions for how to find brake rotors that do not rust.