Is Brake Fluid Corrosive? What You Must Know!

As a car owner, vehicle maintenance is crucial. One aspect that often gets overlooked is the hydraulic system, particularly the brake fluid. So, the question is – is brake fluid corrosive? 

This article will delve into this topic and provide answers regarding the corrosiveness of brake fluids, including DOT 4 and DOT 5, as well as their effects on metal, rubber, paint, and concrete.

Furthermore, we will examine whether brake fluid can cause rust and discuss various brake fluid-related concerns and tips for maintaining your vehicle’s braking system.

Key Takeaways:

  1. Brake fluid is corrosive, but commercial brake fluids contain corrosion inhibitors to protect the hydraulic system.
  2. DOT 4 brake fluid is corrosive due to its glycol ether base and can damage rubber components if not changed regularly.
  3. DOT 5 brake fluid is non-corrosive and resists rust better due to its silicon base, making it a better option for protecting the brake system.
  4. Brake fluid is not corrosive to metal and rubber when used with the proper additives, but its hydroscopic nature can cause corrosion if moisture accumulates.
  5. Brake fluid is corrosive to paint, particularly DOT 3 brake fluid, and can cause damage if not wiped off immediately.
  6. Brake fluid is not inherently corrosive to concrete but can cause corrosion if moisture is absorbed or inhibitors break down.
  7. Brake fluid does not cause rust directly, but accumulated moisture in the fluid can lead to rusting of brake system components.
  8. Regular maintenance, including changing brake fluid and using the correct type, is essential for preventing corrosion and maintaining a safe braking system.
  9. Cleaning up brake fluid spills promptly is crucial to avoid damage to painted surfaces, concrete, and asphalt.

A Deep Dive Into Brake Fluids: The Good, the Bad, and the Ugly

To begin, it’s essential to understand that pure brake fluid is corrosive. However, manufacturers add corrosion inhibitors to commercial brake fluids, ensuring that none of the hydraulic system’s parts corrode.

These additive packages can break down or deplete over time, leaving your brake fluid without adequate anti-corrosive properties.

Modern brake fluid contains special additives, including anti-rust, anti-foaming, and pH balancer additives, that help maintain its performance. In comparison, older brake fluid was primarily affected by moisture seeping in.

Corrosiveness of DOT 4 and DOT 5 Brake Fluids

When it comes to DOT 4 brake fluid, yes, it is corrosive. This glycol ether-based fluid with added borate esters absorbs moisture through the brake hoses, which can corrode rubber parts if not changed regularly. However, it is non-corrosive to all metals and composite materials used in the brake system.

On the other hand, DOT 5 brake fluid contains silicon, making it non-corrosive. It doesn’t absorb moisture and is safe for painted surfaces. In fact, DOT 5 is a better option for rust resistance and longevity.

How Does Brake Fluid Affect Different Materials?

  1. Metal: Brake fluid is not corrosive to metal. However, being hydroscopic, it can absorb air moisture. The moisture in the brake fluid can corrode metallic components of the brake system, so regular fluid changes are essential.
  2. Rubber: Thanks to additive packages, brake fluid is unlikely to corrode rubber. Polyethylene glycol and nitrile rubber are especially resistant to brake fluid.
  3. Paint: Brake fluid is corrosive to paint, with DOT 3 being the most corrosive. DOT 5 brake fluid, being silicone-based, will not damage paint. It’s crucial to clean up any spills quickly to avoid damage. Also read: What to Do if You Get Brake Fluid on Car Paint.
  4. Concrete: Brake fluid is not corrosive to concrete. However, if the fluid absorbs moisture or if the corrosion inhibitors break down, it can corrode concrete. Clean up spills promptly to prevent damage.

The Rust Factor: Does Brake Fluid Cause Rust?

Despite common belief, brake fluid doesn’t cause rust. In fact, it contains anti-corrosive additives that help prevent rusting. However, the fluid’s hydroscopic nature means it can become moisture-prone over time. If not changed regularly, the accumulated water can cause rusting in the brake system components.

Brake Fluid Maintenance Tips

To ensure the smooth functioning of your vehicle’s braking system and prevent any corrosive damage, follow these maintenance tips:

  1. Regularly check your brake fluid levels: Periodically check the brake fluid reservoir to keep the fluid level in the recommended range. Top off with the appropriate brake fluid if necessary.
  2. Change your brake fluid as recommended: Consult your vehicle’s owner’s manual for the manufacturer’s recommended brake fluid replacement interval. Normally, you need to change brake fluid every 2-3 years or after 24,000-36,000 miles, whichever occurs first. However, some high-performance vehicles may require more frequent changes.
  3. Use the correct type of brake fluid: Always follow the owner’s manual for the specified brake fluid. Mixing different types of brake fluids, such as DOT 4 and DOT 5, can lead to system failure or damage.
  4. Test your brake fluid: Use a refractometer or a battery-powered tester to measure the moisture content of your brake fluid. High moisture content can lead to corrosion and reduced braking performance.
  5. Inspect your brake system for signs of corrosion: Inspect brake lines, calipers, and other parts regularly for corrosion or wear signs. Address any issues promptly to prevent further damage or system failure.
  6. Keep your brake fluid reservoir clean: When topping off or changing your brake fluid, ensure that the reservoir and surrounding area are clean to prevent contaminants from entering the system.
  7. Don’t neglect your brake system during routine maintenance: When servicing your vehicle, make sure to include brake system maintenance as part of your routine checks. This will help you catch potential issues before they become more severe and costly.

How to Deal with Brake Fluid Spills

Accidental brake fluid spills can cause damage to various surfaces, including your vehicle’s paint, concrete, and asphalt.

Here’s how to clean up spills effectively:

  1. For painted surfaces: Wipe off the brake fluid as soon as possible using a clean, soft cloth. If the paint is damaged, consult a professional for repair options.
  2. For concrete surfaces: Clean up the spill immediately using soap and water, followed by a degreaser or solvent like paint thinner or mineral spirits if necessary. Avoid using abrasive cleaners or wire brushes that can damage the concrete.
  3. For asphalt surfaces: Treat brake fluid spills on asphalt as urgent, as they can weaken and degrade the surface, leading to cracks and potholes. Use a microbial asphalt cleaner, Coca-Cola, laundry detergent, dish soap, or baking soda to remove the spill. Avoid using pressure washers, solvent-based cleaners, or metal-bristled brooms.

In Conclusion

Knowing brake fluid’s corrosive effects on materials is vital for brake system maintenance and preventing car damage. By regularly checking and changing your brake fluid and following the maintenance tips provided, you can keep your vehicle running smoothly and safely.

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