6 Causes Of Car Battery Corrosion (& What To Do About It)

If you’re wondering why your car battery is corroding, then you’ve found the right article. Not only will you learn about all the different causes of battery corrosion, but you’ll also learn why battery terminals corrode, how to remove corrosion, and how to prevent corrosion in the future. 

So keep reading to find out everything you need to know!

What Causes A Car Battery To Corrode?

If your car battery has started to corrode, there are a few reasons it may have happened. Such as:

Corrosive Gas Leakage

One common reason that your battery may have started to corrode is that corrosive gasses such as hydrogen gas leak out and begin to slowly corrode the metal on your battery and the terminals.


If you have a refillable battery, then it could also be the case that you’ve overfilled it too much, and now the electrolytes are leaking out. Obviously, once the electrolytes leak out, they’ll end up on other parts of your battery, which will then begin to corrode.

Poor Vent Placement

Sometimes where the vents are on the battery can also cause corrosion to occur. If the gas that is coming out of the vents ends up near the metal part of your battery, it’s only a matter of time before it starts to corrode it.


If your battery has been overcharged, then it will begin to heat up. When this happens, more electrolyte solution is going to leak out of the battery, causing corrosion on everything it touches.

One way to tell if your battery is being overcharged is when the corrosion is happening more on the positive terminal.

The Battery Is Being Undercharged

As well as overcharging your battery, undercharging it can also be a problem. When your battery isn’t being charged enough, it won’t be able to accept a charge as well, which can result in corrosion occurring. Mostly on the negative battery terminal.

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The Battery Is Old

Lastly, sometimes corrosion will happen simply because the battery is old. If your battery is 5 years or older, then this is the most likely cause.

Why Do Car Battery Terminals Corrode?

If the battery itself hasn’t corroded, then you may have also noticed that the battery terminals are corroding instead. If that’s the case, then here are all the common reasons that the battery terminals could be corroding.

Rapid Battery Recharging

One cause of battery terminal corrosion is when the battery gets recharged too quickly after being discharged. The most likely cause of this is when your car hasn’t been used in so long, the battery has gone flat. When you jump it and let the engine run, you’re placing a lot of wear and tear on the plates that pass energy from the battery to the engine, which in turn causes it to corrode.

Overfilling The Battery

If you’re topping the battery up yourself with distilled water, you need to make sure that you aren’t overfilling it. Not only will overfilling increase the amount of evaporation, it will also increase the amount of leakage from the battery. Both of which are going to corrode the battery terminals.

Bad Alternator

If you have a faulty alternator, then it could be overcharging or undercharging your car’s battery. Both of these are going to cause the battery terminals to become corroded.

If your batteries are being overcharged, then the corrosion will be on the positive terminal, and if they’re being undercharged, then the corrosion will be on the negative terminal.

High Temperature

If the temperature is too hot, corrosion is also likely to occur. It goes without saying that the hotter the temperature is, the more electrolyte fluid is going to evaporate from the battery. This in turn, will cause corrosion on the battery terminals.

Poor Battery Contacts

If the contacts between the battery terminals and the leads are loose, then it’s going to be a lot easier for corrosion to set in underneath them. And once the corrosion has taken hold, it will begin to grow quicker and quicker.

How Do You Remove Corrosion From A Car Battery And Its Terminals

If you want to remove corrosion from a car battery and its terminals, it couldn’t be easier. Just do the following.

  1. First of all, you should disconnect the battery. Make sure the engine is turned off, and then remove the negative terminal, followed by the positive terminal.
  2. Mix baking soda and water together until you have a paste.
  3. Once you have this paste, use a toothbrush or wire wool to scrub any area that has corrosion building up on them. 
  4. Now that all the corrosion has been removed, the next step is to use distilled water to clean the battery of the baking soda and then dry it thoroughly.
  5. Now you should add petroleum jelly to any of the areas that had corrosion to help prevent it from coming back again.
  6. Now you just need to reconnect your battery. To do this, add the positive terminal first, followed by the negative terminal.

How To Prevent Battery Corrosion In The Future

While you can’t prevent battery corrosion forever, there are definitely things you can do to help your battery last a lot longer. 

Copper Compression Terminals

First of all, using copper compression terminals is a great way to reduce corrosion. They’re made from tinned copper and help ensure the clamp is completely in contact with the battery to stop moisture from getting in.

Anti-Corrosive Sprays

You can also use anti-corrosive sprays on your battery as well. But if you find these too expensive, vaseline and other petroleum-based jellies also do a similar job.

Battery Charging

Make sure you’re always charging your battery correctly. If it’s being overcharged or undercharged, then it will result in corrosion occurring.


Here are some more frequently asked questions that people have about the causes of battery corrosion.

Do You Need To Disconnect Your Battery To Clean Corrosion?

It’s always best to disconnect the battery before you clean away corrosion. Not only is it going to stop you from getting hurt, but it’s also going to make it much easier to spot and remove every piece of corrosion.

Can You Use Wd40 On Battery Corrosion?

WD-40 can be used effectively to help remove corrosion. Just spray some WD-40 onto the affected areas, wait a few minutes, scrub thoroughly and then rinse away. Keep doing this until the corrosion is gone.

How Fast Does A Leaking Car Battery Corrode?

There are too many variables to say how quickly a leaking car battery will corrode, but one thing is for certain, and that’s that it will corrode a lot faster than a well-maintained battery.

How Long Does It Take For A Car Battery To Corrode?

You can expect your car battery to last for 5 years before corrosion becomes too much and it will need to be changed.

Do Car Battery Terminals Corrode If A Car Is Unused?

If you don’t use your car frequently enough, then the battery terminals may end up oxidizing. While this isn’t corrosion as such, it’s just as harmful, and it can prevent your car from starting up when you need it to.

Why Do Car Battery Terminals Corrode In Cold Weather?

Oftentimes, it isn’t the cold itself that corrodes your car’s battery but the accompanying damp weather that gets under the hood. In actuality, more often than not, hot weather causing excess evaporation will be much more corrosive.

What Causes Car Battery Corrosion On The Negative Terminal?

The main cause of a negative car battery terminal corroding is the alternator undercharging it. One of the best ways to solve this is to simply drive your car more.

What Causes Car Battery Corrosion On The Positive Terminal?

Positive car battery terminal corrosion is caused when the battery is overcharged. This is often due to a faulty alternator, so you should get it checked as soon as possible.

Will Running Your Air Conditioner In The Car While Idling Make Your Battery Terminals Corrode?

As long as the engine is running, you don’t have to worry about corrosion on your car’s battery. While it’s not good for fuel consumption, it won’t cause any harm leaving the air conditioner running while idling is completely fine.

Is Mountain Dew Good For Battery Corrosion?

If you plan on removing corrosion from your car’s battery, it is best to stick to a cleaner made for the job or mix baking soda and water together to remove the problem.


As you can see, there are a whole bunch of things that can cause battery corrosion in your car. However, with the right care, you can successfully treat and prevent it from happening again!

If you liked this article, make sure you check out the rest of the website. Otherwise, have a great day!

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