As you look under the hood of your car, you notice some build up around the car’s battery terminals. It is no mystery that what you are seeing is battery corrosion. Car battery corrosion is common and will happen at some point. The corrosion crystals that form can appear white, greenish, or bluish in color. What is going on, you may wonder?
What causes a car battery to corrode? The corrosion that occurs on your car battery’s terminals is from hydrogen gas that is released from the sulfuric acid contained inside the battery.
Once released, the gas reacts and crystallizes with ambient gases in the air to create the white, greenish, or bluish material you see around the battery terminals. Corrosion is not conductive and can prevent your battery from functioning properly.
There are many circumstances in which a car battery may corrode. A car does not have to have been sitting up, not being driven for a long time for a battery to start corroding. In return, just because the car is driven and maintained regularly does not mean the battery will not show signs of corrosion. We’re here to talk more about why corrosion happens and how to prevent it.
What Causes A Car Battery to Corrode?
What is causing the battery corrosion? What does the corrosion mean? Is it something to be concerned about? Well, depending on which terminal and the tint of the corrosion, there are many different answers to those questions. Let’s get into the different reasons for the car battery corrosion, what to be concerned about, and what you can do to prevent the corrosion.
Car batteries may show signs of corrosion slowly over time, or it can build up fairly quickly. Corrosion does typically get more common and prevalent as the battery gets closer to the end of its product life.
Most often, the corrosion that you see on your car battery is from hydrogen gas that is released from the sulfuric acid contained inside the battery leaking out, then combining and crystallizing with other gases in the atmosphere.
Other Types of Car Battery Corrosion
The reason hydrogen gas is formed inside the battery is due to the sulfuric acid cooling and heating up. Other types of corrosion can be due to the types of battery connectors being used. Copper and aluminum connectors react with the sulfuric acid to cause corrosion as well.
Also, if your battery is leaking battery acid, this causes corrosion as well.
How to Determine the Cause of Your Car Battery’s Corrosion
Certain signs will give you an idea of what the cause of the corrosion is. Is the corrosion on the positive, negative, or both terminals? Also, what is the color of corrosion crystals? The answer to those two questions will give you a clue of what exactly is going on and what needs to be done to correct and prevent the continued corrosion.
This is the most common place you will see car battery corrosion. If the corrosion is on the negative terminal, that is typically a sign that your battery is not recharging properly. The crystals will typically be white, and this is common as batteries get older and can be a sign that you will need to soon replace your battery.
You can have your battery at most auto part stores for free to see if that is the reason. It is possible your battery needs to be completely recharged. Here are some reasons that might be behind why your battery isn’t charging properly:
If the battery is not old and you see corrosion on the negative terminals, it might be an alternator problem. Alternators work to help keep your battery charged as it is being used. If the alternator is not working properly, it may not be sending a strong enough charge back to the battery. An auto parts store, when they test your battery, should be able to tell you if the alternator is working properly as well.
There is too much power being consumed by electrical components of your car. This could be from a malfunction that is causing a component such as your air conditioner to drain the battery constantly. An auto parts store’s scan may or may not discover this issue. You may need to take your vehicle to a mechanic to find out if this is the issue and to get it corrected.
Your battery isn’t powerful enough for something that may have been installed. Your new toy may pull too much charge from your battery. The aftermarket amp you purchased or the extra television screens to play movies in the back seat might be causing the corrosion on the negative terminal. If so, you will want to either remove those items or upgrade your battery. Consult with a professional before upgrading your battery, though.
If the corrosion is on the positive terminal, this could be due to overcharging. How could this happen?
Your alternator may be overcharging the battery instead of undercharging.
The battery was overcharged while being hooked up to a battery charger – this is the most common cause of overcharging.
Although there are many battery chargers on the market, if you are giving your battery a complete recharge, I would recommend taking it to a professional. If you insist on doing it yourself, be careful not to overcharge.
If the corrosion is on both terminals, it is probably due to the type of terminal.
Copper will not corrode by itself, but when sulfuric gases are present and with the help of the electrical current flowing through the copper clamps, bluish or greenish corrosion crystals will form.
If the connectors are made of aluminum, the same thing will happen, except the color of the crystals will be white. This is usually a sign that there is a leak of some kind that is allowing the sulfuric gases to escape.
A Word About Electrolyte Leakage
Also, if you see corrosion on both terminals, it may be due to electrolyte leakage. This is rare on a sealed maintenance-free battery but can happen on a battery where you are required to top the electrolytes with water at regular intervals.
If those batteries aren’t maintained properly, or there is damage which allows the electrolytes to leak out, it will cause corrosion r\to form. Also, there is a chance of some of the electrolytes spilling on to the terminals while refilling the battery, and that will lead to corrosion forming as well.
Problems Caused by Car Battery Corrosion
Car battery corrosion is not anything to be too worried about itself. Mostly the battery corrosion is a sign of other problems going on, and by addressing those issues, it will stop most future corrosion. The good thing is that in most cars, the battery is located in a location that is easily accessible, so it is not hard to keep a check on the corrosion.
The only problem with the corrosion itself is those corrosion crystals are not very conductive and work to slow or limit the charge going from or into the car battery.
Over time it can get to the point that your car may have difficulty starting or keeping a good charge. This may cause you to need to get your car jumped off. This is common and can be easily fixed by cleaning the corrosion from the battery. Once clean, the corrosion is gone, and without that resistance, your battery should start back performing as expected.
How To Clean Car Battery Corrosion
Car battery corrosion can be cleaned from the car battery using some common household goods. If you have made it this far, you already know where your car battery is located, but if not now is the time to find your battery. Refer to your car manual if the location isn’t immediately obvious.
It is recommended to use safety glasses and work gloves to help avoid any accidental injuries while cleaning off the corrosion from the car battery. Also, avoid touching the corrosion with bare skin and be sure you are doing the cleaning in a well-ventilated area.
First, remove the terminal covers and disconnect the connectors from the battery posts. Loosen the bolt using a wrench and remove the connectors from the battery posts. Start with the negative terminal then the positive terminal. Red is the positive terminal, and black is the negative terminal. Avoid touching the two connectors together while disconnected.
Inspect your cables and connectors. This might not aid in cleaning the corrosion off, but the reason to clean corrosion is to keep your battery in good working order, so it makes sense to do other types of maintenance as well. When inspecting the connectors, make sure the cables are secured properly to the connector.
See if the insulation, which is the rubber or plastic casing around the wires, has become dried, peeling, or cracked in areas. If the copper wiring is exposed to the elements, this will cause the copper to become brittle. This will limit the current flow and cause problems with your car starting and undercharging, so change the cable as needed.
Use your cleaning agent of choice and an old toothbrush or wire brush to clean the corrosion off the battery terminals and connectors. A solution of 3 parts baking soda and 1-part water works well. You can also use lemon juice or vinegar mixed with a little water or any type of carbonated soft drink. FYI: Most carbonated drinks contain carbonic acid, which helps to clean off corrosion and can aid in removing rust deposits.
Here's how I cleaned my nut and bolt for the car battery connector. I soaked them in white vinegar and added salt to help speed up the process. It turned out pretty good after I let them sit over night.
It all depends how much corrosion has developed on the part you are cleaning, when determining how long you should soak it in liquid or with a paper towel. Some people might prefer to use a Dremel to scrub off tough problems, but it wont work on the thread of nut and bolts.
If the corrosion is difficult to remove, do not try using force. Instead, either place the connectors in a cup of the cleaning solution and allow to soak or if it is the battery terminals themselves, either soak a soft towel or tissue paper in the cleaning solution and cover the battery terminals where the corrosion is for about 20 minutes. The corrosion should come off easily then. If not, just repeat the soaking step again until all corrosion is removed.
Rinse then dry all areas you just cleaned. Hopefully, you know water and electricity are not a human-friendly combination, but if not, here is a reminder of that fact. Thoroughly rinse all parts with water to remove any remaining solution or corrosion. Then dry with a soft towel or paper towel. Make sure all parts are dry before proceeding to the next step.
Reconnect the battery. Now that all the pieces are clean and dry reconnect the battery, and that should solve any starting problems that the corrosion may have been causing. Attach the positive terminal then the negative terminal. Also, there are several things that can be done during this step to help prevent future corrosion. I have several tips below that aid in preventing corrosion.
Tips to Prevent Corrosion
Now that you understand what car battery corrosion is and how to clean it, let’s look at ways to prevent it from happening.
1. Petroleum Jelly
Petroleum jelly can be applied to the connectors and terminals after cleaning. After cleaning the corrosion off and reconnecting the battery, apply a generous amount of petroleum jelly to that area.
The petroleum jelly will keep any future corrosion from forming and can be easily reapplied as needed whenever the coat of jelly starts to wear thin.
2. Commercial Products
There are many different battery corrosion preventative sprays and brush-on compounds on the market available for purchase. These work very similar to petroleum jelly in that you clean and reconnect the battery first and then apply the product as directed.
I used dielectric grease to help prevent corrosion on the terminals and the connectors.
3. Battery Charging
If the battery is either undercharging or overcharging, take your car to professional to find out what the cause is and have that corrected. If the problem is undercharging due to heavy usage from certain items, consider disconnecting those.
If you want to keep using those items, talk to a professional about possibly upgrading the battery because you need to be sure your car’s alternator will be able to adequately work with a different battery. Also, the physical size of the battery may be too big for the area for a battery in your car.
4. Proper Maintenance
Some batteries need regular maintenance. If so, keep your battery properly maintained. Regular car maintenance is also important in keeping all aspects of your car running properly, so do not forget any other types of services your car may require regularly.
Other issues can cause other problems that create car battery corrosion as a by-product of those issues. The alternator may need replacing after 100K miles.
Keep in mind many things may cause your car to undercharge, which can lead to corrosion, as you know by now.
5. Battery Terminal Protectors
Battery terminal protectors are small pads that fit between the connector and the battery. They are usually made from some type of material that prevents corrosion from forming, such as felt. They are relatively cheap and are an easy way to prevent corrosion from happening.
To install battery terminal protectors, disconnect the connectors from the terminal and simply slide the battery terminal protectors over the terminal and reconnect the battery. Do not forget to disconnect the negative terminal first and but to reconnect the positive terminal first.
6. Copper Compression Terminals
Copper compression terminals are made from tinned copper and are specially made so that the clamp fits snugly onto the terminal. This works to limit corrosion from forming in places that would limit the current going from the battery to connectors and on to the rest of the car. These are also some of the best terminals available on the market to purchase.
7. Battery Usage
Another way to help prevent car battery corrosion is to limit battery use when the car is not running. When you are sitting in the car without it running but still listening to the radio or charging your phone, your alternator is not working, so your battery is undercharging.
Nobody wants to waste gas, as I was told by my parents growing up repeatedly, but I guess this means that keeping the car running to listen to the radio while parked in the front was not wasting gas. I was helping to save their battery. I still do not believe they would look at it that way now, though.
8. Check Your Battery
Routinely check your battery to look for any signs of corrosion. If you start to see some forming, then take the necessary steps to clean the corrosion away. Also, consider why it was forming and take the correct measures to fix what is the cause or apply one of the many products that help prevent corrosion.
9. Keep the Posts And Connectors Clean
Dirty posts and connectors can lead to a loss of conductivity between the two. This can lead to undercharging of the battery, which will cause corrosion. If the posts and connectors are dirty, disconnect them and give them a good cleaning. Be sure everything is dry, though, before reconnecting them.
10. Check Your Battery Cables and Connectors
Check the insulation of your battery cables for areas that are dried, cracked, or peeling. Exposed copper wires do not hold well to the elements and will become brittle, and this will limit current flow, causing undercharging, which will lead to corrosion.
Also, make sure the cables are attached to the connectors properly. If there is not a good connection there, this will also cause corrosion. If needed, replace cables or reattach them to connectors if loose. If the connectors look damaged, replace them.
11. Make Sure You Are Using the Correct Battery
If you bought your car used, there is a chance the battery in the car may not be the correct battery for that particular make and model. Also, if you have added aftermarket speakers and amps, the old battery may not be strong enough for that added burden.
Talk to a professional mechanic or visit an auto parts store, and they will be able to tell if you have the correct battery for your needs.
How to Deal With a Leaking Battery
If your battery has a leak that is causing the sulfuric acid to escape, you will need to replace your car battery. You will also clean to the battery compartment itself before installing the b\new battery in that area to prevent further corrosion.
Don’t forget to use safety glasses and work gloves to help avoid any accidental injuries while cleaning off the car battery compartment. Also, avoid touching the corrosion with bare skin and be sure you are doing the cleaning in a well-ventilated area. Here are the steps to clean the car’s battery compartment.
1. Remove the leaking battery. Remember to disconnect the negative terminal first, then the positive terminal when removing the leaking battery. Place the leaking battery in a plastic bag and dispose of properly. Many auto parts stores will do this for you.
2. Clean out any leaked sulfuric acid. Get some paper towels to clean up any sulfuric acid that may have leaked out. Dispose of those paper towels properly and avoid contact with your skin.
3. Wipe away any corrosion. Use a soft cloth wet or wire brush with a cleaning solution to remove any remaining corrosion in the car battery compartment. You can use a solution of 3 parts baking soda and 1 part water or just regular white vinegar.
4. Clean the connectors. Using the same solution and either a soft cloth, wire brush, or cotton swab and make sure the connectors are clean and free of any corrosion. If the corrosion is difficult to remove, do not use “elbow grease.” Place the connectors in a cup of the cleaning solution and allow them to soak or for about 20 minutes. The corrosion should come off easily then. If not, just repeat the soaking step again until all corrosion is removed.
5. Dry the battery compartment and connectors. Using a clean, dry cloth, make sure the battery compartment and connectors are free of any excess moisture left behind from the cleaning before installing a new battery.
Battery Care and Maintenance
Battery care and maintenance have been touched on briefly throughout, but for those who have skimmed over the article, let me sum everything up here for you. Keeping your battery well maintained will extend the life of the battery and keep your car starting correctly. This will also, in turn, keep corrosion down to a minimum. It will also keep from putting too much strain on the alternator.
Test your battery regularly. As batteries get older and closer to the end of their service life, they get weaker and not recharge correctly. Eventually, your car will fail to start. Replace your battery sooner rather than later once you see the battery is getting weaker. That last bit of use isn’t worth the aggravation of being stranded somewhere with a car needing a jump.
Plan your replacement. Most batteries have a life of 3 to 5 years. When you purchase one, ask about the warranty and expected life. Make that a consideration when selecting a battery, then plan to replace it at the end of the warranty. You can go back to the same auto parts store you bought the battery to have it tested regularly.
Install battery terminal protectors. Battery terminal protectors cost just a few dollars. They are small felt pads and will prevent corrosion and improves the electrical connection between battery and cables. They are quick and easy to install.
Secure your battery. Over time hold-down brackets and battery base clamps may loosen or wear down. This will start your battery moving and vibrating, which shortens the battery’s life. Inspect these parts regularly and replace these parts as needed. If needed, there are kits to give added security or support. These parts are relatively inexpensive and are quick and easy to install.
Inspect cables and connectors. Make sure the cables are secured properly to the connector. Inspect the insulation of the cables to see if there are areas that have become dried, peeling, or cracked. Tighten connections and replace connectors and wires as needed.
Install a car battery maintainer. If you have a car that sits for extended periods or you only take for short limited trips, a car battery maintainer is for you. Unlike a traditional car battery trickle charger that never shuts down, a car battery maintainer tests the battery at regular intervals. If the battery needs a charge, it will charge the battery up and then sit idle until it is time to the battery again.
Taking care of your car’s battery is fairly easy and will prevent problems from happening in the long run. The sight of corrosion is no reason to get scared, but it is something you need to take care of. Clean it off, apply something to prevent it from happening, and have your battery tested to see what was causing the corrosion. If needed, replace your battery. Here’s to happy, corrosion-free driving!