How to Clean Battery Corrosion Safely

Corrosion happens under every car hood, but if ignored, it can come between you and starting your car. Use baking soda and distilled water to clean battery corrosion. Then brush it away carefully.

If a car battery works long at all, you’ll eventually see a soft, white or green powder growing on a battery terminal or two. Corrosion is natural for all batteries. Normally, it isn’t a big deal at first. Left unchecked, corrosion can build up between the terminals and the clamps. If enough of the powdery corrosion gets in there, it can suppress the flow of electricity while chewing up the parts.

Given how many problems it can cause, it’s easy and important to clean battery corrosion carefully.

Steps on How to Clean Battery Corrosion

1. Safety first. Put on safety glasses and gloves. Make sure you have good airflow around you.
2. Hook up backup power. If you’re cleaning a car battery, connect the memory saver. Obviously, you don’t have to worry about this if you’re cleaning a power tool or flashlight.
3. Disconnect the battery. Cover the positive terminal and pull it away from the battery to make sure they don’t accidentally touch.
4. Prepare the neutralizer. Mix the baking soda and water, either in a cup or on the brush. Don’t do this on the battery case itself.
5. Slow strokes at first. Use the plastic brush first to sweep big chunks of corrosion off the top of the battery. Work the baking soda into those chunks to neutralize them.
6. Brush away from vent caps. Avoid getting any of your mixture into any raised vent caps or holes at the top of the battery.
7. Scrub the metal. Use the wire brush on the battery posts and metal terminals, even if you can’t see corrosion on them.
8. Neutralize anything left. Apply extra water and baking soda as needed to neutralize the corrosion around the battery case.
9. Dry the top thoroughly. Wipe down the terminals and top of the battery case. Again, make sure none of the baking soda-water mixture goes inside the battery case.
10. Reconnect the battery. Connect the red positive terminal first, then attach the ground.

The Supplies You Need to Clean Battery Terminals from Corrosion

• Baking soda and hot water. Heated water mixed with baking soda will neutralize the corrosion so you can safely brush it away.
• A wire brush. Use this when cleaning the lead battery posts and the car’s clamps.
• A plastic brush. Nylon brushes for cleaning dishes would work well, but you could use a toothbrush, too. (Just throw it away afterward.)
• A towel or rag. You will need to dry the battery and terminals after clearing the corrosion.
• Gloves and eye protection. Plain sunglasses could work if you don’t have any protective eyewear.
• A well-ventilated space. Do it outside, in the open garage or with a fan blowing away from you.
• A memory saver for cars. If you’re cleaning a car battery and its clamps, you’ll need to disconnect it — but disconnecting without a memory saver can cause expensive electrical problems. (They’re available online for $9 to $20.)

With these supplies, you’ll be well equipped to clean corrosion from batteries as big as a car battery or as small as the AA in a toy car. However, the baking soda mix needs to be a little different because of what you’re cleaning.

Ways to Mix Baking Soda to Clean Battery Corrosion

Mix the baking soda and water differently based on what you’re trying to clean.

Cleaning corrosion off small electronics like a flashlight or power tool?

• 1 tbsp baking soda
• 1 cup warm water
  Dip a cotton swab in to soak up the watery mixture.

Cleaning a corroded car battery?

• 4 tbsp baking soda
• ¼ cup warm water
  Scoop the toothpaste-like mix onto a brush.

What Is Car Battery Corrosion and How Do You Stay Safe When Cleaning It?

Hydrogen gas causes most of the car battery corrosion you see. It’s odorless, colorless and nontoxic to people — but it’s corrosive to metal. That’s why you need to cover your hands and eyes when dealing with car batteries.

Green or white powder growing on a battery post is chemistry. Hydrogen, with its single proton and single electron at the top of the periodic table, reacts easily with most metals. Tiny doses of hydrogen gas will gradually corrode most metals, including steel, copper and yes, lead.

And you don’t want to touch it. Nitrile gloves can protect your hands, and any kind of eyeglasses can protect your eyes. On top of that, staying in a well-ventilated area keeps you from inhaling stray particles of corroded metal.

But isn’t the corrosion caused by battery acid?

Well, what you call “battery acid” isn’t just acid.

The liquid inside a car battery is a mix of sulfuric acid and water. When the battery recharges or drains down, the liquid changes. If you recharge a battery, the liquid becomes more acidic. If you use a lot of power, it becomes mostly water. Passing a current through the battery (and the liquid inside) is what makes the electrolyte swing from more acidic to less acidic.

Something else happens when you pass a current through water: electrolysis.

An electric current in water splits water into hydrogen gas and oxygen. Some car batteries have vent caps to let those gases pass harmlessly out of the car (but you need to refill those with distilled water.) Others are sealed, holding onto the gases until they can recombine with the electrolyte, and only a safety valve will let some gas out.

Any hydrogen gas leaving the battery can interact with the first bit of metal it bumps into. That could be the lead battery post, an aluminum terminal clamp, copper wiring, etc. Sometimes, it can interact with a bit of sulfur and carry it out of the battery. That hydrogen sulfide can later react with other metals. It’s a microscopic amount of sulfuric acid mixed in with the hydrogen — but enough that you don’t want to touch corrosion.

Better Than Baking Soda: More Professional Products for Cleaning Battery Corrosion

Battery Corrosion Cleaner. Shake it up and spray it on corrosion. After a few minutes, you can brush it away.

Corrosion Preventative. Spray this after cleaning corroded terminals to prevent new corrosion from forming quickly.

Dielectric Grease. Cake it on after you reconnect the battery and it’ll seal out anything that would interrupt the flow of electricity. It doesn’t conduct electricity, so don’t put it between the post and the clamp. If your clamps have any exposed wiring, a layer of this can prevent corrosion from creeping up the wire under the rubber.

Battery Post Brush. Imagine a thimble the size of a battery post, except with dozens of metal bristles inside. While handy and does the job in a pinch, it’s not especially necessary if you only clean your car battery once or twice a year.

WD-40. You can use WD-40 on battery posts because it works its way into corners to neutralize corrosion, but it’s not ideal. If you can’t clean it out, then it becomes tomorrow’s grime.