How To Clean Corroded Battery Terminals: A Complete Guide

Car battery corrosion is caused by a chemical reaction where the vehicle’s battery acid from the inside is reacting with the metal on the outside of the battery. When you notice the corrosion, you may even see a whitish substance around the battery terminals, don’t ignore it.

There are several causes for this condition which mean that corrosive liquids from inside the battery are reacting with the metal on the battery terminals. Clean it off immediately, if left there it can prevent the terminals from conducting properly, and ultimately your car would fail to start.

Recognizing Car Battery Corrosion

The copper clamps that are connected to the battery are often the place where you will notice changes. All car batteries contain a mixture of sulfuric acid and water. This reacts with lead alloy plates inside the battery. The old-fashioned batteries have removable caps for topping up the acid solution with distilled water as the level gets low.

The caps have tiny vents allowing some acid to leak out if the battery is overfilled. Once this solution touches the battery terminals or cable contacts, corrosion starts to occur. This is when you will notice the white powdery deposits around the car battery’s terminals.

A wrench is used to remove corroded battery terminal.

We all need automotive batteries to start our cars, as without the battery, the car wouldn’t run. The voltage supplies a spark for the internal combustion engine to start up, as well as powers the wipers, lights, and radio. The bigger and more powerful the car, the bigger the battery will be.

What Problems Does Car Battery Corrosion Cause?

Car batteries don’t last forever and once they deteriorate it is better to get it replaced or the car will become unreliable. There are 8 different types of automotive batteries and depending on the type of battery in your car you may not have any corrosion present.

Battery corrosion is not normal and can be avoided by making longer trips which allow the alternator time to fully recharge. Checking the fluid levels in the battery is also recommended. Unfortunately, many of us don’t drive very far, home, school, and work maybe just a 5-minute trip not long enough to charge the alternator.

Once corrosion occurs and reaches the battery terminals it can certainly cause the car not to start. The two terminals are Copper Sulfate (positive terminal ) and Lead Sulfate (negative terminal) reduce the conductivity including to the plates within the battery. This is a vicious cycle, lead sulfate starts in the battery due to undercharging and an imbalance within the battery.

Any corrosive build-up will limit the efficiency and lifespan of your battery, and if you are working on removing the corrosion, it is important to wear rubber gloves as the battery acid can burn your skin. When cleaning the corrosion off in your driveway, on completion of the work, hose the driveway thoroughly as you don’t want any residual acid lying around where your pets and children play. We don’t want the lead sulfate going into the waterways and causing harm to the environment.

Most major cities have mobile battery change services where, for a fee, a man drives up and installs a new battery in your car, and takes the old one away. If you are time-poor, this is often the best option to keep you on the road.

How To Remove Car Battery Corrosion

If you have corroded battery terminals, one day the car just won’t start. So when you first notice the deposits appearing is the best time to clean them off, not when they have been there for months. As we know that they reduce conductivity, and you may need to purchase a new battery when the problem has gone too far.

If you are planning to remove the corrosion from the battery yourself, you need to be properly dressed. Wear old overalls, eye protection, and rubber gloves, full PPE (personal protective equipment). Acid burns are highly irritating to the skin and will eat into skin and clothing, if any gets on your skin, rinse the area under cold running water. Allow plenty of time to clean the corrosion off the car battery as you want to be sure that it is properly done.

Before you start the clean-up, disconnect the battery from the vehicle. Pliers may be needed to do this. To remove the copper sulfate using baking soda and water made into a paste, scrub the paste using an old wire brush or nail brush. Leave the paste on for 2 minutes, and then clean it off with a damp rag. Be careful not to get the solution into the cells of the battery, as this will ruin it.

Some people suggest that you use WD-40, however, this does not neutralize the corrosion which is what we are aiming to do. If you have a science degree you will realize that neutralizing the corrosion is important. Clean and tighten the connections to the battery. If you notice any car battery corrosion check your alternator.

To Avoid Car Battery Corrosion

  • Go for a long trip to avoid battery corrosion from occurring, do this every month.
  • Invest in a home battery charger.
  • Put Vaseline (petroleum jelly) on the terminals after you have cleaned them to prevent build-up from reoccurring.
  • Try to avoid the damage from happening to start with.

What Causes Car Battery Corrosion?

  • Old age you may have kept the battery too long.
  • It might have been overfilled by a family member.
  • Chemicals could have eroded the copper clamps.
  • Hydrogen gas may have been chemically released, leading to corrosion.
  • Electrolytes might be leaking from the battery.
  • The battery may have been overcharged.

Technology is leading to new and better batteries all the time, and if you feel there is a problem with your battery, get it checked, as the car won’t start without a battery. Battery problems don’t always result from batteries but can be caused by a faulty alternator and this can be checked at the same time.

5 Ways To Prevent Car Battery Corrosion

1.     Take Longer Trips

When you get a new car try to take some longer trips, as this is the easiest way to recharge your battery. Short trips are not efficient for the life of the battery. If your battery has become totally flat, take a drive of 30 minutes to one hours duration depending on how discharged your battery is.

When the roadside assist is called because your battery is flat, this is what they recommend, so time to drive to one hour when the battery has been flat. This may happen when the car has been in the garage for a while when maybe you are away on an extended holiday or alternately when you have left the internal light on in the car and flattened the battery.

2.     Check Battery Fluid Levels

Check your battery’s fluid level at least every month, and if you find that the levels are low, overcharging might be occurring. Once that battery is charged add only distilled water using a 5 ml syringe to avoid overfilling. Carefully fill each cell, stopping when the water level is just below the fill tube. If you don’t feel able to do this yourself, ask your mechanic to do it for you, as it is important.

Mechanic watering a car battery.

3.     Don’t Overcharge The Battery

If using your home charger be careful not to overcharge the battery. This can be very damaging both to the car and the battery. It is far better to go for that long drive down the highway to charge up the battery naturally. When you see corrosion on the terminal, it can mean that the battery is probably overcharging. Once you have cleaned it off, apply the dielectric grease to the battery posts.

Do a controlled overcharge every few months, especially if the corrosion has been noted. The corrosion started on the inside of the battery, and you want it gone. If you have the right charger it will have a desulfation setting, and you can use this to bring your battery back to good health with the controlled overcharge.

Before you embark on this procedure read all the directions carefully to avoid errors. When you are doing this, it is best that the car is out in the driveway and not in the garage. As gases may be escaping and they won’t be so toxic in the outdoors. You will probably have some questions about this process and you may want to comment or ask what happens next?

4.     Consider Buying An Electric Vehicle

The Lithium batteries used in an electric vehicle last for years, and are recyclable making them a great environmental choice. They are also lighter than the conventional battery and don’t seem to cause any problems. On reading the literature, Lithium batteries can last for 20 years without needing to be replaced.

Electric vehicle charging station.

The problem seems to lie with how long you can drive on a single charge, often about 150 miles, and if you just use the car for home, work, and school, the Electric Vehicle with a Lithium battery may be the answer for you. The electric vehicle is charged at the designated recharging stations, often located in big Shopping Centers. Hybrids are becoming a lot more popular with many families purchasing one.

5.     Don’t Keep Your Battery Too Long

Car batteries don’t last forever, and if it is beginning to fail, it is best to get a new one. Batteries come in different sizes, so choosing the right size is also very important, as the wrong size won’t fit properly into your vehicle.

If you want to change to a different type of battery, consult an expert mechanic to ensure that it is the right choice for your car. If you have decided to purchase a new battery, phone a home mechanic service to come to the house and put the right battery into your car.

Mostly car battery corrosion can be avoided, but when in doubt definitely change the battery, as after a few years it will reach the end of its life.

Car Battery Corrosion Keeping Your Car Safe

Because your car is used to transport your family around from place to place, it is important to keep it in good mechanical working order and the battery is no exception. If you have a garage keep your car there to protect it from the elements as both winter cold and summer sun can age your car fast.

Cars are quite expensive, often being the third most expensive item we ever buy, and although we don’t want to keep them for too long, sometimes we have to. After a couple of years, wear and tear start to happen, and this is when we want to pay attention to our battery.

Check your car battery reserve capacity and the reserve capacity indicates how long a battery will run a vehicle if the charging system fails. It measures the number of minutes that the car will continue before the battery is totally flat. This is useful knowledge, especially if you are out of town.

While not entirely necessary to do this yourself, have the mechanic test the battery’s ability to hold voltage, especially if you are going on a long trip during the school holidays.

A Flooded Lead Acid Battery

Does not mean there is anything wrong with the battery but is a term for the oldest type of battery still in common use, and the most affordable type to purchase and starts quickly. It is used to power standard vehicles and accessories.


If you take good care of your battery, car battery corrosion will probably never occur. But like most problems you need to be aware of what can happen and how to fix it if does occur.

If you live in an area of high humidity near the ocean, it is important to have a garage as the sea air penetrates your car and seems to get into everything including the battery, so check under the bonnet regularly for deposits causing car battery corrosion.

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About Brock Rangel

Hi, I am Brock, and I am the lead editor/photographer for TheCarColony. I have been a mechanic for over 14 years now, and I am here to spread my car knowledge across the web!

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