What Causes Corrosion On a Car Battery Terminal?

close up photo of vehicle engine

You would not want your car to refuse from starting on a long deserted highway or your in-car electronics to fail, in a traffic jam. If your car battery has corrosion on its terminals, you will be risking the above.

This is because your car battery serves the all-important purpose of feeding the starter, which powers on the engine. More so, the sound system, touch screen control, and automatic doors also use the car battery.

Any kind of corrosion in your car battery will affect the ignition as well as the electronic paraphernalia, putting you in unnecessary hassles.

Thankfully, fixing the car battery corrosion not only prevents such troubles but is also quite easy. By the end of this article, you’ll know why corrosion takes place, how to get rid of it, and how to prevent it from occurring in the first place.

What is Car Battery Corrosion?

Car battery corrosion is the by-product of a chemical reaction taking place at the terminals of the car battery. It generates a powdery substance that deposits on the terminals and is blue-ish white in color.

This corrosion is basically a result of the battery’s chemicals interacting with the gasses being released from inside the battery. It’s a natural process that occurs on its own accord. Corrosion on different terminals of the battery represents different things.

Negative Terminal

Corrosion on the negative terminal takes place when your battery is undercharging. This usually happens when the vehicle is not being driven enough, and the battery is not receiving ample charging.

The most common example of this is the Lead-Acid battery. The negative terminal of the Lead-Acid battery exhibits a process called Sulfation, resulting in the formation of Lead Sulfate (the corrosive material).

Positive Terminal

The positive terminal starts corroding when the battery is being overcharged. In case, the car is being driven around for long hours, or a manual charging effort leads to overcharging, the positive terminal will corrode.

The key reason behind this is the reaction between the Copper present in the battery clamp and the Lead present in the terminal. They react to form Copper Sulfate which obstructs the flow of current to the car, hence, poor battery performance.

Reasons For Car Battery Terminal Corrosion

Car Battery Corrosion

The best way to prevent car battery corrosion is to have a fair idea of the reasons behind it. There are multiple factors that corrode your car’s battery. The following are the top reasons that you should always take care of.

Electrolyte Spillage

Most car batteries contain a liquid inside them such as Sulphuric Acid or Water, to facilitate the chemical reaction. You must have seen the car mechanics replace the liquid in your car battery from time to time. If yes, you also have an electrolytic battery.

Due to irregular maintenance or excessive liquid refill, the liquid tends to spill from the battery terminals. This results in the perfect condition for the corrosive reaction to take place, and the terminals begin to corrode.

Charge Disbalancing

The car batteries extract their charge from the car’s internal charging system, which means they get charged and discharged repeatedly.

Every battery has a healthy charging threshold which must be optimally fulfilled. Both the cases of charging the battery above or below the threshold will lead to corrosion.

As we learned earlier, overcharging means corrosion at the positive terminal and undercharging means the negative terminal gets corroded.

This disbalancing of charge usually takes place when the vehicle is not being properly driven around.

Hydrogen Discharge

Your car’s engine heats up and cools down multiple times a day, which results in the release of Hydrogen gas from the battery. As this gas is trapped under the bonnet, it starts reacting with the battery terminals, giving rise to battery corrosion.

It’s one of the most common ways of corrosion. The phenomenon occurs in batteries that use Sulphuric Acid as an electrolyte.

Ageing Battery

As batteries age, they naturally corrode due to many of the reasons listed above. After 4-5 years of regular usage, the battery will tend to corrode vigorously. This is because the factors causing corrosion multiply and the battery goes out of the maintainable condition.

You will notice that old batteries corrode faster and are harder to fix. Therefore, if your battery is causing trouble too often, it’s a good time to get a new one.

Problems Caused By Battery Corrosion

close up photo of classic car

On a wrong day, car battery corrosion can escalate from a hitch to a nightmare very quickly. If you’re troubleshooting the car engine all by yourself, you must know the scenarios wherein the car battery is the culprit.

Engine Starting Troubles

A misfiring engine is the most common and direct effect of car battery corrosion. The corrosion hampers the battery terminals from conducting electricity properly, leading to low voltage transfer to the starter. This means, even after several efforts, your car engine just won’t power on. This can further damage the starter which in most cases will invite a mechanic workshop visit.

Failing Electronics

Your in-car electronics such as the sound system, electronic rearview mirrors or automatic car doors are dependent on the car battery. When the battery is unable to serve an ample amount of voltage to these electronics, they get faulty and can break down in the middle of the ride.

Malfunctioning Transmission

The car’s transmission system also co-depends on the car battery for optimal functioning. Most cars come with a computerized system to manage the car battery and the transmission. When the transmission doesn’t get enough power from a corroded battery, it can throw intermittent problems. The most common being a delay in the gear shift. A troubled transmission may result in gears shifts being completely misplaced, resulting in unapprehended consequences.

How To Fix Car Battery Corrosion

Fixing battery corrosion is all about getting the chemistry right, and it’s quite easy in the practice. Most corrosion takes place due to chemical reactions and knowing how to balance them out is the key.

Following are a few ways by which you can fix the corrosion eating up your car batteries.

Baking Soda Solution – For Mild Corrosion

Baking Soda or Sodium Bicarbonate that you’ll easily find in the kitchen is a great anti-corrosive reagent. Mix baking soda in water to create a solution and pour it slowly on the battery terminals.

Use a wire brush or a spare toothbrush to scrape off the corrosion from the terminals. Make sure the car engine is not ignited when you’re doing this. The baking soda solution reacts with the corrosion to loosen it up from the surface of the car battery.

Once the corrosion has been swept away, clean the battery terminals with water. Wipe the terminals with a cloth and you’re good to go.

Soda Water – Corrosion Quick Fix

If baking soda isn’t around, a soft soda drink can also be used. In case you’re out on the highway, this alternative can act as a quick fix.

Turn off the engine and just pour the soda water or the soft drink on the battery terminals. Let it stay for a while as you see the corrosion dissolving off. Once it’s gone, you can clean it with a sponge or a soft cloth.

Make sure you don’t bathe the terminals in the soft drink, just a little bit will be enough in most cases.

Baking Soda Immersion – For Extreme Battery Corrosion

In case the above two methods fail, you have a serious case of corrosion. In order to deal with this, we’ll take out the copper battery clamps and immerse them in a baking soda solution.

You can do this by dipping the clamps in a cup full of soda water solution. Alternatively, you can also wrap tissue paper soaked in soda water, around the terminals.

Let the copper clamps stay there for 20 minutes. Most of the corrosion will flake off. In case it doesn’t you’ll need new battery clamps.

How Can We Prevent Corrosion?

Prevention is always the smarter thing to do. When it comes to car batteries, you can take some measures to reduce the rate at which it corrodes. Only drastic levels of battery corrosion cause serious problems.

If you’ve recently bought a new battery, the following measures will help you extract a prolonged life from it.

Corrosion Preventive Materials

To your delight, commonly found grease and Vaseline are great at preventing corrosion at the battery terminals. It’s advisable to apply a small amount of any of the materials from time to time, in order to stop excessive corrosion deposition. You can also go for anti-corrosive sprays that are easier to use and far more effective. These materials disallow the corrosive reactions from occurring.

Resolve Battery Charging Issues

You’ll be able to figure out by looking at the terminals if improper charging is causing the corrosion. There will be deposition on either of the terminals, indicating overcharging or undercharging.

In such a case, you should always seek the help of a mechanic to figure out the exact reason behind the charge imbalance. It could be your AC, which is leaving too little charge for your battery. Or some electrical fault that is flooding the battery with extra charge.

Regular Maintenance

The best advice is to get your car the maintenance it deserves. Battery corrosion occurs naturally, hence, catching it well in time will save the battery for good. Try to be as punctual with your car servicing schedule, so that such problems can be well caught in time.


Ensure smooth rides, safe road trips and well-maintained car health by actively dealing with battery corrosion. As promised, by now you have actionable knowledge on how to spot, fix and prevent a corroding battery. Remember the trouble of going through an engine breakdown is much more than the trouble of fixing the battery. Hence, do it whilst you still have time.

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