Symptoms
- Powdery white, blue, or green buildup on terminals
- Hard or intermittent starting
- Dim lights or flickering electronics
- Terminal feels loose under the crust
Likely causes
- CommonNormal battery gassing over timeBatteries naturally release small amounts of hydrogen gas that react with terminal metal.
- PossibleOvercharging or a failing batteryA battery being overcharged can corrode terminals faster than normal.
- PossibleLoose terminal connectionA loose clamp can arc slightly and accelerate corrosion buildup.
- Less commonBattery leak or crackA damaged battery case can leak acid and cause heavy corrosion.
What to do
- Turn off the car and disconnect the negative (black) terminal first, then the positive (red).
- Mix a small amount of baking soda with water to neutralize the corrosion.
- Use a wire brush or old toothbrush dipped in the mixture to scrub the terminals and clamps clean.
- Rinse with a small amount of plain water and dry thoroughly with a rag.
- Reconnect positive (red) first, then negative (black), and tighten clamps snugly.
- Apply a thin layer of terminal grease or petroleum jelly to slow future corrosion.
- Inspect the battery case itself for cracks, swelling, or leaking, which mean it needs replacement.
- If corrosion returns quickly after cleaning, have the charging system tested for overcharging.
Tools and parts
- Wire brush or old toothbrush
- Baking soda
- Water
- Rag
- Gloves and eye protection
- Wrench for terminal clamps
Battery terminal protector spray or greaseSearch: “battery terminal anti-corrosion grease”
Replacement battery (if damaged)Search: “car battery for [your car make model year]”
When to call a pro
If the battery case is cracked, swollen, or leaking fluid, don't clean it yourself; have it replaced by a shop or parts store.
Safety
Use caution
Battery corrosion can contain acid residue; wear gloves and eye protection and avoid touching your face while cleaning.