How Corrosive is Brake Fluid Really?
3 Answers
Generally, brake fluid is highly corrosive, but high-quality brake fluid significantly reduces corrosion and rust on various metals, thereby extending the lifespan of the brake pump. However, using inferior brake fluid can quickly corrode metals, posing risks to driving. Below are introductions to two types of brake fluids: Glycol Ether-Based Brake Fluid: Primarily composed of polyoxyethylene ether compounds, supplemented with lubricants, diluents, rust inhibitors, and rubber inhibitors, it is the most commonly used brake fluid in automobiles worldwide. Most products are classified as DOT3, with a few reaching DOT4. This type of brake fluid offers high equilibrium reflux boiling points, low viscosity at low temperatures, excellent rubber compatibility, and relatively low metal corrosion. The downside is that glycol ether-based brake fluid tends to absorb moisture from the air, forming low-boiling azeotropes that reduce high-temperature performance. Additionally, as moisture content increases, low-temperature viscosity rises significantly, impairing low-temperature performance. Moreover, moisture ingress can enhance the fluid's corrosiveness, accelerating metal corrosion in the braking system. Glycol Ether Borate-Based Brake Fluid: To improve equilibrium reflux boiling points and reduce hygroscopicity, research has found that ester-based brake fluids meet these requirements, especially when borate esters of polyglycol ethers are used, significantly mitigating the impact of moisture on the boiling point of glycol ether-based brake fluids. This category of brake fluid is generally classified into DOT4, Super DOT4 (V4), and DOT5.1.
I've been repairing cars for over a decade and witnessed numerous brake fluid corrosion scenarios. This stuff is highly destructive to automotive components. When it contacts car paint or plastic parts, it can cause bubbling and peeling in no time, and rusts metal even faster. Rubber hoses become softened by corrosion and prone to leakage, leading to brake failure and dangerous accidents. The corrosiveness comes from acidic substances formed when brake fluid absorbs moisture and deteriorates - the longer it's left, the worse the damage. I recommend changing it every two years to prevent excessive water content. Always wear gloves during operation and wash immediately if it contacts skin. Regularly check the brake system for any leakage signs. Never underestimate corrosion risks - if brake fluid leaks and corrodes critical components, the pedal might sink during emergency braking, directly compromising driving safety. Always handle with extreme care.
As someone who enjoys DIY car maintenance, I've found that brake fluid is indeed highly corrosive, especially noticeable on paint surfaces—just a single drop can quickly strip away the top layer of paint. It also poses potential damage to metal and rubber components, and prolonged neglect can corrode brake lines, leading to delayed or failed braking. The key is to regularly inspect the fluid's condition: discoloration or cloudiness indicates increased corrosion risk. During replacement, handle with care—wash off any spills on skin immediately to minimize irritation. Routine maintenance suggests changing it every two years to prevent moisture absorption (which increases corrosiveness) and reduce unexpected repair costs due to corrosion. Safe driving starts with attention to detail—addressing brake fluid issues promptly is essential.
