How to Clean Corroded Battery Terminals

Difficulty: Beginner Time: 15–20 minutes

That white, blue or green crust on your battery terminals is corrosion, and it blocks electricity. It can make the car crank slowly, click without starting, or keep the battery from charging, even when the battery itself is fine.

Cleaning it takes about 15 minutes and costs almost nothing. Before you buy a new battery or starter for a no-start, this is the first thing worth trying.

What you'll need

Step by step

1. 1

   Turn off the car and open the hood

   Park on level ground, turn off the engine and remove the key. Find the battery and its two posts: positive (+, usually red) and negative (–, usually black).

2. 2

   Disconnect the negative (–) cable first

   Loosen the nut on the black negative clamp and twist the cable off the post. Move it aside so it cannot touch the battery.

3. 3

   Disconnect the positive (+) cable

   Lift the red cover if there is one, loosen the clamp and remove the positive cable.

4. 4

   Mix baking soda and water

   Stir about a tablespoon of baking soda into a cup of water. It neutralizes the acid in the corrosion.

5. 5

   Scrub the posts and clamps

   Dip the brush in the mix and scrub the battery posts and the inside of both cable clamps. It will fizz; that is the acid being neutralized. Scrub until you see bare, shiny metal.

6. 6

   Rinse and dry

   Wipe or lightly rinse away the residue with a little clean water, keeping water away from the battery caps. Dry everything completely with a rag.

7. 7

   Protect the terminals

   Spray the posts with terminal protector, or rub on a thin coat of petroleum jelly. This slows new corrosion.

8. 8

   Reconnect positive (+) first, then negative (–)

   Put the red positive cable back on and tighten it, then the black negative cable last. Tighten until the clamps cannot twist by hand.

9. 9

   Start the car

   Try starting the car. If it starts normally, the corrosion was the problem. If it still clicks or cranks slowly, have the battery and alternator tested.

Tips

• If corrosion keeps coming back quickly, have the battery and charging system tested. Overcharging or a leaking battery can cause it.
• Felt anti-corrosion washers that slip over the posts are cheap and help prevent buildup.
• Most auto parts stores will test your battery, starter and alternator for free.

Parts and tools that may help

Enter your year, make and model on the store's site to see parts that fit your car.

Car batteryPick up or ship · Advance Auto Parts

Jump starter packPick up today · Advance Auto Parts

Battery chargerPick up today · Advance Auto Parts

Battery terminal cleanerPick up or ship · Advance Auto Parts

MultimeterPick up today · Advance Auto Parts

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Frequently asked questions

Can corroded battery terminals stop a car from starting?

Yes. Corrosion blocks the flow of electricity, so the starter may only click or crank slowly even with a good battery. Cleaning the terminals often fixes it.

Can I use Coke to clean battery terminals?

It can loosen corrosion, but it leaves a sticky sugar residue. Baking soda and water works better because it neutralizes the acid, and it rinses clean.

What causes battery terminal corrosion?

Small amounts of acid vapor escape from the battery and react with the metal. It builds up faster on older batteries, in hot weather, or when the battery is being overcharged.

Should I disconnect the battery to clean the terminals?

Yes. Take the negative cable off first and put it back last. That way a slip of the wrench cannot cause a short circuit.

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