Symptoms
- Chalky white or blue buildup around the battery posts
- Car is slow to start or has intermittent electrical issues
- Dim lights or radio resetting occasionally
Likely causes
- CommonNormal battery off-gassing over timeBatteries naturally release small amounts of hydrogen gas that reacts with moisture and metal to form corrosion.
- CommonLoose terminal connectionA loose clamp allows more arcing and moisture intrusion, accelerating corrosion.
- PossibleOvercharging or a failing batteryExcess gassing from an aging or overcharged battery increases corrosion buildup.
What to do
- Turn off the car and, if possible, disconnect the negative (black) terminal first, then the positive (red).
- Mix a small amount of baking soda with water to make a paste, which neutralizes the acidic corrosion.
- Scrub the terminals and clamps with an old toothbrush or a terminal cleaning tool using the paste.
- Rinse with a small amount of plain water and dry thoroughly with a rag.
- Reconnect the positive terminal first, then the negative, and tighten both clamps firmly but not overtight.
- Apply a thin coat of dielectric grease or a felt anti-corrosion washer to slow future buildup.
Tools and parts
- Wire brush or terminal cleaning tool
- Baking soda
- Water
- Wrench
- Gloves
- Safety glasses
Battery terminal protector spray or felt washersSearch: “battery terminal anti-corrosion spray”
When to call a pro
If corrosion returns quickly after cleaning, or the car struggles to start even after cleaning, have the battery and charging system tested.
Safety
Use caution
Battery corrosion can contain sulfuric acid residue; wear gloves and eye protection, and avoid touching your face while cleaning.