Battery Terminal Corrosion – How To Fix It?

Battery Terminal Corrosion – How To Fix It?

Have you noticed battery terminal corrosion? If so then it is important to fix the problems as it can lead to further issues with your car’s electrical system.

Battery terminal corrosion often looks like a bluish or whitish substance that is stuck to the battery terminals. It is usually a sign that something is not right with your car’s battery or the alternator.

The battery is one of the most important components. Not only does it function to ignite the vehicle but it also allows you to listen to the radio, and controls things like the AC as well as the headlights.

Using the same car battery for years is one of the factors that cause battery terminal corrosion. Let’s find out about other major factors and what you can do to fix them.

For easier navigation throughout this post. Feel free to use our table of contents below.

Corrosion On Battery Terminal

corrosion on battery terminal

Several factors could cause corrosion on the battery terminal.  

1. Leaking Of Hydrogen Gas

The acid inside your car battery is turned into an electric current. Hydrogen gas is the byproduct. If this car battery leaks out of the battery in spaces around the car terminal, it will react with the atmosphere and cause terminal corrosion. 

This can show that there is a problem with the battery charging and is either overcharging or undercharging. 

2. Leaking Electrolytes

Lead-acid batteries are more prone to corrosion caused by electrolyte leakage. The odds of corrosion caused by electrolyte leakage goes up whenever you overfill the car battery with battery water. 

That said, when the electrolytes leak into the terminal they will cause terminal corrosion. 

3. Chemical Reactions With Copper Clamps

The terminal clamps are usually made of copper. This material doesn’t corrode easily. However, whenever electricity passes through the clamps, it causes a chemical reaction and produces copper sulfate as the by-product. 

When this copper sulfate comes into contact with the sulfate of the terminals, it causes corrosion of the terminals. 

One way to tell that copper sulfate is the reason for the terminal corrosion is by finding a bluish precipitate on the terminals. When there is an accumulation of copper sulfate on the battery terminals, you will begin to have trouble starting your car as the copper sulfate is not a good conductor of electricity. 

4. Overcharging

corrosion on positive battery terminal

Terminal corrosion can also be a result of the alternator overcharging your battery. For a proper charge, the alternator should not go above 14.5 volts. 

To find out if this is the case, ignite your vehicle and let it rev then use a multimeter to gauge the amount of current going to your car battery. 

If it is above 14.5 volts, then it’s important to have the problem fixed by a mechanic. 

5. Overfilling The Car Battery

When adding battery water, you may make the mistake of overfilling it which may, in turn, cause the electrolytes to leak. As we saw earlier when these electrolytes come into contact with the car battery terminals, it results in corrosion. 

While not all car batteries require battery water, it is imprinted to ensure that you do not overfill the battery. 

Corrosion On Positive Battery Terminal

Corrosion in the positive terminal of your car battery is often caused by overcharging. When there is excessive current running through the terminal clamp, which is made of copper, it releases a copper surface that reacts chemically with the terminal to produce corrosion.

Corrosion in the positive battery terminal will appear as a bluish-green or whitish substance. This is copper sulfate. Some battery terminal clamps are made from aluminum.

When it reacts with the lead and the terminal it creates aluminum sulfate. This will appear as a whitish substance in the positive terminal.

Over time the corrosion greatly affects the quality of the battery.

Corrosion On Negative Battery Terminal

corrosion on negative battery terminal

While corrosion on the positive terminal is a result of overcharging, that on the negative terminal is often a sign of undercharging.

Undercharging of the car battery often occurs when there is an issue with the terminal or if there wasn’t sufficient running time allowed to charge the battery.

You can follow the steps below to clean corrosion from the negative battery terminal.

Whether corrosion occurs in the positive terminal or it occurs on the negative terminal, the effects are the same in that it results in poor electrical conductivity and damage to the battery.

It will also cause failure to start the engine.

Corrosion On Battery Terminal And Car Won’t Start

One of the most frustrating situations is getting into your car, and trying to start the car only for the car to fail to start. If you are pressed on time and you need to get somewhere fast it can be frustrating trying to figure out what the problem is.

One of the main factors that could cause your vehicle to fail to start is corroded battery terminals. Corrosion can occur on the positive terminal due to overcharging and can occur on the negative terminal due to undercharging.

But as we saw above the are multiple other reasons why corrosion would occur. Corrosion will prevent the free flow of electric current from the battery terminals to the rest of your car.

Before you decide on replacing the battery, it is a good idea to clean out the corrosion and see whether this fixes the issue.

Using a toothbrush and baking soda and water solutions you should be able to clean out the corrosions. Use a clean cloth to wipe clean the car battery terminals. Then try and start the car.

If your car starts smoothly, then that means that electricity can once again flow through the car battery terminals and into the rest of the car.

However, if you clean the car battery terminals and still the car won’t start, then it’s time to take your phone and call your auto mechanic. The issue could be deeper than you thought.

Battery Terminal Corrosion Prevention

You know what they say, prevention is better than cure. By preventing battery terminal corrosion, you can ensure that your car always works at an optimum. 

Preventing corrosion can also end up saving you plenty of cash that you would have otherwise spent on car repairs

Here are a few things that you can do to prevent battery terminal corrosion. 

1. Get A New Car Battery

If the car battery lasts longer than 5 years, it may start to develop leaks. Leaking acid or electrolytes could cause corrosion on the terminals. 

It is therefore advisable to get a new car battery every 5 or so years (and considering how long does a car battery last). 

2. Install Copper Compression Terminals

Replace your aluminum or copper terminal clamps with copper compression terminals. These are top-quality terminals that are designed to ensure that the terminal comes to contact with the clamps. 

The clamps, on the other hand, are made of tinned copper which also helps prevent terminal corrosions. 

3. Check The Battery Charging

Car battery overcharging or undercharging are just some of the things that cause corrosion in the battery terminals. 

Head to your car’s manual and identify the correct charge for your car battery. Also, put your car in rev and use a multimeter to calculate the voltage that is reaching your battery. 

If it is above 14.5 volts, then this is a clear sign of an issue with the car’s alternator. Have this looked at by the mechanic before it causes more damage to the car. 

4. Use Anti-Corrosion Products

Products such as anti-corrosion sprays can help prevent the battery terminal corrosion from occurring in the first place. 

If you have some Vaseline or grease then you could also apply those to the battery terminals to prevent corrosion from happening. 

How To Clean Battery Corrosion

Now that you understand the cause of car battery terminal corrosion, let’s now take a look at how you can fix the problem there are several ways that you can do this. 

1. Using Baking Soda

One of the most effective ways to remove the copper sulfate from the car battery terminal and other battery connections is using a solution of baking soda and water. You will also need a wire brush. 

Before you can even apply this solution the first step is to ensure that the ignition is turned off. Then take out the terminal clamps and use the bare brush to take out most if not most of the corrosion. 

Next, take the baking soda water solution and pour it onto the terminal then use the brush to clean out the corrosions. 

Having done this thoroughly, use a clean cloth to wipe clean the terminal. Apply wheel grease on the terminals to prevent further corrosion.

2. Soda

If you do not have any baking soda close, then you can always opt for soda. The reason soda is so effective a removing corrosion from the battery terminal is due to the carbonic acid contained in the soda.

Pour the soda on the corroded terminal and then use a cloth to wipe it clean. 

3. Soaking To Get Rid Of Heavy Corrosion

If there is heavy corrosion on your battery terminal. Using a brush may not be enough. Take the baking soda water solution and use this to soak the terminal. 

Remember to always disconnect the negative terminal first and ensure that the ignition is turned off. Let it soak for 20 minutes and then use the toothbrush to clean the corrosion. 

Repeat the process with a new baking soda water solution and let it soak for another 20 minutes. Clean the corrosion with a brush and then clean again with fresh water. 

Wipe the terminal with a clean cloth and ensure it is competing dry. Next, apply grease to stop the corrosions. 

Disconnect Car Battery Order

There is no denying that the car battery is one of the most important parts of your vehicle. 

The car battery serves two main purposes in your car. First off, it provides the required electric current to start your vehicle

Secondly, the car battery helps to power the car’s electric system which includes the radio, the dashboard lights, the headlights, and even the window control bottoms

It makes sense therefore that for your car to perform at its optimum the car battery should also be in top form. 

Terminal corrosion is just one of the common problems that cause car batteries to fail. This can be due to several factors such as leaking electrolytes, leaking car battery acid, overcharging, and undercharging the car battery. 

To clean the battery terminals you will need to disconnect the car battery. You may also need to disconnect the battery due to several other reasons such as the need to replace an old battery with a new one.

So is there a right and a wrong way to disconnect and connect the car battery? The answer is yes. Let’s find out. 

Safety Tips To Observe When Disconnecting The Car Battery

Before you can disconnect your car battery, here are a few safety measures to observe. 

Remember that your car battery stores an electric charge. This means that you can get shocked if you handle it the wrong way. Before you can disconnect the car battery ensure, that you are not wearing metal such as rings or bracelets. If the terminals come into contact with these metal pikes it can cause a shock

The battery contains gases and acid which can be harmful when inhaled. This is why it is important to ensure that you only connect the car battery in an outdoor space. 

Avoid at all costs working in a moist or damp environment, instead remove your car better in a clean dry space. 

Steps To Disconnecting The Car Battery

You can disconnect your car battery in 7 simple steps as shown below. 

Step 1: Turn Off The Ignition Key

Before you can even touch the terminal clamps, make sure that you have turned the car completely off and taken out the keys from the ignition.

Ensure that you have left the car door open as the battery has charge and can cause the doors to lock when removing keys. Also, ensure that you have the gear set in drive if it’s an automatic, and if you drive a manual car, ensure the gear is in first gear. 

Step 2: Opening The Hood

locate the battery

Now you need to reach the car battery and to do that you will need to open the hood. Some cars have a lever situated somewhere around the steering wheel. Other cars use a button. 

While other cars have the engine in the trunk which means in this case you will need to open the trunk. Simply refer to your car’s user manual if you get a bit confused. 

Step 3: Access Your Car Battery

Now that you have opened the hood, you will need to get to the front of your car and open the hood then keep it open using the opening rod to keep it open. Having done this, find your car battery and look for the negative t



The negative terminal will usually have a black covering or it will have a negative (-) sign on top of it.

If you are having a hard time locating your car’s battery or finding the negative terminal, refer to your car’s owner’s manual. 

Step 4: Disconnecting The Negative Terminal

Once you can locate the negative terminal the next step will be to disconnect it. You must always start with the negative terminal. This reduces the chances of speakers or even the chances of the battery exploding

Use a wrench to loosen the nut that tightens the terminal clamp. Then using safety gloves, remove the negative terminal by hand. Also, ensure that you place the negative terminal clamps in a safe place to prevent any shorting. 

Step 5: Disconnecting The Positive Terminal

Just like with the negative terminal, use a wrench to loosen the nut that opens the positive terminal clamps. Be careful to wear protective gloves to protect yourself from any shocks. 

Remember that as you disconnect the positive terminal, there may be a charge left in the car’s electric system so ensure that the positive terminal doesn’t come into contact with the metal part of the car to prevent any disruptions to the car’s electrical circuit 

Step 6: Locate The Battery Bracket

If you want completely replace the battery or take out the battery, simply locate the battery bracket or the battery step that is located at the bottom of the battery. 

Use a spanner to loosen the nut in the battery bracket. 

Step 7: Changing The Battery

Having loosened the battery strap or bracket you can now pick up the battery from the battery tray gently. Keep in mind that the car batteries especially if you are driving a truck can be heavy so make sure you can lift the car battery yourself. If not you can always enlist help. 

Now that you have the old battery removed you can repeat the process of installing the new car battery in reverse. Place the car battery in the battery tray, and fasten the battery strap or bracket. 

Next, connect the positive terminal and then connect the negative terminal. Remember that you will need to reset the vehicle’s clock as well as add the radio settings after this. 

Battery Corrosion Facts: How to Clean and Prevent it

  1. Corroded battery terminals are a common cause of reduced battery life and electrical problems in vehicles.
  2. Corrosion is a white, blue or greenish powder typically surrounding one of the battery terminals, posts or cables with a granular, powdery texture.
  3. Car battery corrosion can happen due to the normal release of hydrogen gas, age, overheating, or leaking fluid.
  4. Before cleaning battery corrosion, ensure your safety by wearing heavy-duty gloves and eye protection.
  5. To clean battery corrosion, start by disconnecting the battery and inspecting the cables for damage.
  6. You can neutralize and remove corrosion using a commercial battery terminal cleaner or a baking soda and warm water solution.
  7. After cleaning, dry and polish the battery casing, posts and terminals before reconnecting them securely.
  8. To prevent or slow down corrosion, coat the battery terminals with dielectric grease or battery terminal protector.
  9. Corrosion on the positive battery terminal can be a sign of overcharging while corrosion on the negative terminal can be a symptom of undercharging.
  10. Regular maintenance on all systems, including your car’s electricals, is essential for the health and longevity of your vehicle.

Frequently Asked Questions

Here are some popular FAQs:

What Causes Battery Corrosion

Several reasons could cause battery corrosion such as alternator overcharging, acid leak, electrolyte leaks, as well as undercharging of the car battery. 

What Causes Car Battery Corrosion On Positive Terminal

Having corrosion on the positive terminal is often due to the alternator overcharging the battery. You can find out by putting the vehicle on revv and using a multimeter to gauge the voltage. If it is more than 14.5 volts then you should have the car checked by a mechanic. 

How To Remove Battery Corrosion

You can remove battery corrosion using a solution of baking soda and water and a toothbrush. Simply disconnect the terminals starting with the negative terminal. Pour the solution and scrub using the brush. Repeat this until the terminal is completely clean and use a clean cloth to wipe clean the terminal. If you don’t have quick access to baking soda, you can repeat the steps above using soda. 

How To Prevent Battery Terminal Corrosion

There are several ways that you can prevent battery terminal corrosion such as applying grease or vaseline to the terminals after cleaning them. You can also use an anti-corrosion spray. Have the car’s alternator checked to prevent overcharging. 

How To Disconnect Car Battery

To disconnect the car battery, turn off the ignition and remove the keys. Open the hood and locate the battery and then disconnect the negative terminal. Next, disconnect the positive terminal. If the terminal clamps are too tight use a spanner or wrench to loosen the nuts then move over. You should also have safety gloves on to prevent shock as the car battery stores charge. Ensure that the positive terminal doesn’t come into contact with any metal part.

How To Remove Car Battery

To remove the car battery start by disconnecting the negative terminal and then the positive terminal. Reach out to the bottom of the car battery and locate the battery bracket. Loosen the bracket and you can now safely remove the car battery. 

How To Clean Battery Acid

If the corrosion on the battery is caused by a leaking of acid, you can clean the acid using a neutralizing solution such as white vinegar. Use a cloth to dab the white vinegar on the terminals. If the stains are stubborn, you can use a toothbrush dipped in white vinegar. If you don’t have fast access to vinegar you can use lemon juice. 

What Is Battery Acid

The car battery is essentially sulfuric acid that has been diluted with water to bring down the acidity to 37%. Sulphuric acid is used in lead-acid batteries acid. That’s said, the level of acidity depends on the brand. 

What Color Is Positive On A Battery

Every car battery comes with two terminals. One is marked as positive and one is marked as negative. The positive terminal is marked red. 

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