4 Causes Of Blue Stuff On Car Batteries (& How To Fix It)

If you’ve noticed blue stuff on your car battery, then you may be wondering what it is and whether it’s harmful to your car or not. In this article, not only will you find out what the blue stuff on your car battery is, but you’ll also learn why it’s there, what to do about it, and other frequently asked questions!

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

What Is The Blue Stuff On Your Car Battery?

If you notice blue stuff on your car battery, the battery terminals, and even around the battery, then you’re dealing with corrosion. When the battery begins to leak it releases anhydrous copper sulfate, which is white in color. Once the anhydrous copper sulfate gets wet however, it becomes blue.

So long story short, the blue stuff you see around your car battery is corrosion.

Why Is There Blue Stuff On Your Car Battery?

There are a number of different reasons that corrosion is occurring on your battery, and it’s starting to become covered in blue stuff. It could be any of the following!

An Overfilled Battery

One reason that your battery might have blue stuff on it is when it’s been overfilled. If there’s too much electrolyte solution, then it will begin to leak out and react with the metal parts of the battery corroding them.

Overcharging Or Undercharging The Battery

It may also be the case that the battery is either being overcharged or undercharged as well. When your battery is being overcharged, you’ll tend to notice more blue stuff on the positive terminal, and when it’s being undercharged, you’ll notice blue stuff on the negative terminal.

Leaking Electrolyte Solution

If you’re using a lead acid battery and it’s getting old, then it may just naturally begin leaking more with time. When this is the case, the best solution is to simply buy another battery.

Leaking Hydrogen Gas

Lastly, whenever your battery is being charged, it’s going to create hydrogen gas. When the hydrogen gas escapes the battery it’s going to cause a build up of corrosion around the battery. 

Novosibirsk, Russia – February 08, 2019: Toyota Highlander, close-up of the engine, front view. Photography of a modern car on a parking in Novosibirsk

How To Clean The Blue Stuff On Your Car Battery

If you’ve noticed blue stuff on your battery, then of course, the best thing to do is clean it off as soon as possible. To clean it completely, you’ll need to do the following:

Disconnect The Battery

Before anything, the first thing you’ll need to do is disconnect the battery. Make sure when you’re doing this the car is turned off and you’re wearing your safety equipment. 

To disconnect the battery use a socket wrench and start with the negative terminal first. (It will be the one labeled with a‘-’ and it will also be black in color.)

Once you’ve done this, you’ll then need to disconnect the positive terminal which will be red in color and have a ‘+’ on it.

Check The Battery For Damage

Now that your battery has been fully disconnected, you can begin to inspect it for damage. Look for anywhere with white/yellow/blue stuff building up as all of these colors indicate corrosion. 

You should also check the battery case and make sure that it isn’t cracked or bulging. If you do notice that it has begun to bulge or cracked in places, then you’ll need to replace it. 

Neutralize The Acid

Once you’ve found all the spots that have been damaged by corrosion, it’s time to neutralize the acid. The easiest way to do this is to just use baking soda, however, you can also buy battery cleaner too.

If you plan on using baking soda, just mix with two tablespoons with a small amount of water, until you’ve created a paste. Once the paste has been created you just need to use it in combination with a toothbrush to clean the corroded parts. 

You’ll begin to notice that as you place the baking soda paste onto the corroded areas it will begin to fizz. This reaction is actually the acid being neutralized. 

After you’re done scrubbing the affected areas, you should use a wire brush to give the metal a nice shine, and helping a clear connection form between the wires and the battery.

Rinse The Battery

Now that the battery acid has been neutralized you can begin to rinse it and remove the leftover residue. To do this, use a dry rag and start with the terminals and connectors before moving to any other areas of the battery that had blue stuff on them.

Once you’ve completely cleaned the battery, you should then rub petroleum jelly on the battery terminals, to help slow down corrosion in the future.

Reconnect The Battery

And now all that is left to do is reconnect the battery. However, this time you should connect the positive cable, and then connect the negative cable. Make sure you tighten the bolts correctly, and then your car will be good to go again!

How Do You Prevent Blue Stuff On Your Car Battery?

The best way you can prevent blue stuff on your battery is to simply make sure you’re taking proper care of it. So if you need to top it up, make sure you’re not overfilling. You also make sure that your alternator isn’t faulty, and that you’re keeping the battery as dry as possible.

And if you do notice corrosion on your battery, you should remove it as soon as possible, to stop it spreading further.

(Find out what the white stuff on your car battery is.)

Why Won’t Your Car Start When There Is Blue Stuff On The Battery?

If your car won’t start when there’s blue stuff on the battery, then it could be due to any of the following reasons.

  • The blue corrosion has built up so much that electricity can no longer flow properly from the battery to the rest of the cars
  • Sometimes corrosion occurs when there is a problem with the alternator. If the alternator has been faulty for a while, then it might have caused the battery to die.
  • And lastly, it may simply be the case that the corrosion has affected the terminal, and they are no longer connected securely.


Here are some more commonly asked questions that people have about blue stuff on their batteries!

Does Car Battery Corrosion Mean That The Battery Is Bad?

If you notice corrosion on your battery it doesn’t mean it’s gone bad yet, but you should clean it immediately, to reduce the chances it will need to be replaced.

In fact, even if your battery doesn’t seem to be supplying your car with power, once you remove it (especially around the terminals), then it may start to work again.

Why Is Blue Stuff On The Positive Battery Terminal?

If there is blue stuff on the positive battery terminal, then it’s a sign that the battery is being overcharged. As well as being blue, you may also notice that the corrosion is blue, white, or greenish too.

Why Is Blue Stuff On The Negative Battery Terminal?

If you notice blue stuff on the negative battery terminal, then the chances are the battery isn’t being charged enough. If this is the case, it means there could be a problem with the alternator, or perhaps you’re not running your car for long enough each time you use it. 

Why Is There Blue Foamy Stuff On Your Car Battery?

If the corrosion appears foamy, then it’s just the same as the rest of the blue stuff you find on your battery. If you notice it, you should use baking soda and water to remove as much as possible.

Why Is There Blue Powdery Stuff On Your Car Battery?

The corrosion on your battery can also appear as blue powdery stuff as well. You’ll most likely notice this sort of corrosion around the terminals of your battery.

Why Is Blue Stuff Coming Out Of Your Car Battery?

If you notice blue stuff coming out of your battery then it could be because corrosion is happening inside and leaking out. If this happens, you should consider purchasing a new car battery.

Are There Any Other Colors On A Battery That Can Cause A Problem?

As well as being blue, corrosion can appear in a number of different colors as well. The corrosion can also appear brown and rusty, white, or green.


As you can see, blue stuff on your battery is a concern, but with the right care, you can make sure that your battery is back to performing at it’s best in no time!

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

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