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Why Car Battery Terminals Corrode?


Why Car Battery Terminals Corrode?

Corrosion is something that can happen to many different parts of your car for different reasons. Something as simple as road salt can cause parts of your car to begin to rust, but car battery terminals aren’t affected by the ordinary reasons for corrosion. 

Car battery terminals corrode naturally due to hydrogen gas interacting with the lead in your battery terminal. Corrosion can also occur when the battery is too full, battery fluid leaks, or battery charges for too long. 

Let’s go into more details about battery terminal corrosion and what you can do to prevent it.

What Causes Car Battery Terminal Corrosion?

The heating and cooling of sulfuric acid causes car battery terminal corrosion. Naturally, corrosion can occur when sulfuric acid heats and cools and produces hydrogen gas. Sometimes we cause corrosion in our car battery terminals by overfilling or overcharging the battery as well. 

Let’s break down each potential cause of car battery terminal corrosion in more detail. 

Hydrogen Gas

Car battery terminals contain sulfuric acid. When the battery is charging or discharging, the sulfuric acid begins to heat. When you heat or cool sulfuric acid, it produces hydrogen gas. 

This is a natural part of the process of charging and using your car battery, but it can cause corrosion over time. This is because the hydrogen gas will sometimes interact with lead in your car’s battery terminal, which causes it to corrode.

Read: How Long Can a Car Battery Sit Unused? 

Overfilling Causes Leaking

This won’t apply to all car batteries, as not all of them are refillable. For the ones that are, overfilling can be something that causes the car battery terminal to corrode. Excess liquid can make its way outside of the battery and come in contact with the car battery terminal. 

Corrosion happens when the liquid seeps out and comes in contact with the battery terminal. Overfilling is a great way to make sure this happens. So, make sure if your battery needs refilling, that you don’t overfill it. 

Read: Does a Car Battery Drain Faster In Cold?


Overcharging your battery can cause corrosion as it causes the electrolytes in the car battery to experience too much energy and begin to move around too fast. The movement of the electrolytes causes a lot of heat because of the more intense and quick movement. 

When the heat and the movement begin to be too much, hydrogen gas will begin to leak from any opening in the battery. As discussed above, hydrogen gas mixing with the lead in the car battery terminal can cause corrosion. 

How Can You Prevent Car Battery Terminals From Corroding?

You can prevent car battery terminals from corroding by not overcharging the battery, using an anti-corrosive spray, and checking the battery regularly. Whatever your choice for prevention, make sure that you’re keeping an eye on your car battery to ensure you catch corrosion early. 

Let’s take a closer look at the ways to keep your car’s battery terminal from corroding. 

Not Overcharging the Battery

As we discussed above, overcharging your car battery can cause your battery terminal to corrode. The best way to stop this from happening is to be careful not to overcharge the battery. 

You can prevent issues with overcharging by ensuring you charge the car battery in a cool, shaded place. Excess heat from an outside source like the sun can cause the car battery to overcharge and get hot too fast. 

Another way to ensure that you don’t overcharge your car battery is to ensure your alternator is in good working condition. If your alternator is running too fast, it can cause your car battery to overcharge, which leads to corrosion. So, test your alternator regularly by doing it yourself or taking it to your mechanic. 

Read: Can You Put a Different Size Battery In Your Car?

Anti-Corrosion Spray

Anti-corrosion spray is a great method for preventing corrosion on your car battery terminal. It works by adding a protective layer to your car battery terminal, which helps it prevent corrosion. 

The reason that anti-corrosion spray works so effectively is that it adds a layer on top of the car battery terminal. This separates the hydrogen gas from the lead that is on the battery terminal. 

If you’re looking for a good option for anti-corrosion spray, check out the CRC Battery Terminal Protector (available on It boasts its ability to protect the car battery terminal  without the use of lead. So, you can ensure that the hydrogen gas that forms won’t cause corrosion with the use of this spray as it adds another layer. 

Check the Car Battery Terminal Regularly

Another great way to prevent corrosion is to check your car battery terminal frequently for corrosion. Once it starts, it’ll keep accumulating until it’s difficult to remove. So, the best way to stay on top of corrosion is to catch it early. 

If you do spot corrosion on your car battery terminal, then you should take care of it right away. It may be best to also ensure that you use other preventative measures like spray and not overcharging, as discussed above. 

How Can You Reverse Car Battery Terminal Corrosion?

You can reverse car battery terminal corrosion with a baking soda and water mixture. Just make sure that you apply the substance while the car is off and cooled down. Alternatively, you can apply drinking soda to the area and scrub away the corrosion.

If car battery terminal corrosion is something you’re already experiencing, then we have some solutions for you. It’s always best to keep an eye out and try to catch it as soon as possible, but it’s not always realistic. So, let’s talk about how to get rid of it if you already have it. 

Read: Car Full Service Cost // Whats included?

Baking Soda

Combining baking soda and water is a great way to get rid of corrosion. Always make sure that you turn your vehicle off before attempting to clean the corrosion off of the battery terminal. Then, apply the baking soda and water mixture. 

For a light amount of corrosion, then the mixture should be enough. For heavier amounts of corrosion, you may need to apply this mixture and scrub the corrosion off with a brush. A toothbrush would work best in this situation, but a sponge or something similar would also get the job done. 


You can also use ordinary drinking soda to get rid of small amounts of corrosion if baking soda is unavailable. The amount of acid in soda can be a decent substitute for baking soda. Though, soda will require more scrubbing. 

Whichever option you choose, make sure that you clean the surface of your car battery terminal with just water after cleaning off the corrosion. After doing this, you may want to consider applying anti-corrosion spray or oil to keep it from happening again in the future. 

Is Corrosion Different From Rust?

Corrosion is different from rust, though rust is a type of corrosion. Corrosion is the effect of oxidation on metals and non-metals, while rust is the presence of air and moisture causing oxidation in iron. 

Some people use corrosion and rust interchangeably, but this isn’t necessarily accurate. Rust is a type of corrosion but not all corrosion involves rust. Rust only affects iron and its alloys. It doesn’t affect other surfaces. 

The main difference between corrosion and rust is how it can happen. For rust to occur, you need air and moisture to be present. Without moisture, rust can’t happen. The same doesn’t apply to corrosion. 

Corrosion doesn’t involve moisture. Instead, it’s the reaction of air or other chemicals exposed to a surface. In the example of car battery terminal corrosion, corrosion is when hydrogen gas comes in contact with lead. There’s no need for moisture to be involved for this process to occur. 

You’ll know the difference between corrosion and rust not only based on the material that you are working with but also how it looks. Corrosion creates many different shades of blue and green. The color will change based on the amount and the involved chemicals. Rust is a mix of brown and orange. 

Read: Car Diagnosis Cost

Final Thoughts

Car battery terminals can corrode due to human error like overcharging and overfilling, or it can happen naturally over time. As the battery cycles through charging periods, the sulfuric acid inside heats up and cools down, producing hydrogen gas that leads to corrosion. Thankfully, you can treat the corrosion using baking soda, water, and a toothbrush.

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