Battery Terminal Corrosion: Why it Happens & How to Fix It!

Battery terminal corrosion can happen because of electrolyte or hydrogen gas leakage, overcharging or overfilling the battery and chemical reactions in the copper clamps

A car battery is the most important part of a car for the smooth operations of the car’s electrical facilities. 

However, battery terminal corrosion prevents the electricity flow to the car battery and creates problems in operating the radio, headlights or the ignition. In order to fix the battery terminals, you first need to know what causes it.

To drive a car without any issues, you should stop the battery terminals from corroding. We’ll let you know about battery terminal corrosion and why it happens and how to fix it.

Battery Terminal Corrosion: Why it Happens & How to Fix It

Battery terminals are made of heavy duty metals or lead and have minimum electrical resistance. It connects the battery to the electrical components of the car. So, battery terminal corrosions can lead to engine failure as well as several failed systems within the car.

Detecting a terminal corrosion is pretty easy. If a white, green or blue thing starts covering the cables or terminals of your battery, then the terminal is corroded. 

There could be a few possible reasons for this corrosion. We’ll list them below:

Electrolyte Leakage

All car batteries consist of liquid and electrolyte components. Over time, the battery can get damaged and acquire cracks and holes. If your lead battery is damaged, it can cause battery fluid leakage. 

It mostly affects lead acid batteries but Lithium ion batteries in hybrid cars can cause electrolyte leakage too. This leaked electrolyte will run down and gather in the battery terminals and slowly form corrosion over the battery terminals.

Accidentally spilling some electrolyte while refilling the battery water can lead to terminal corrosion too. The electrolyte will chip away the battery terminals over time.

Hydrogen Gas Leakage

In electrolyte batteries that operate with sulphuric acid, hydrogen gas leakage is a fairly common cause of battery leakage. The engine of the car produces hydrogen gas throughout the day because of overcharging or undercharging. 

This gas could get trapped inside and come in contact with the battery terminals. Hydrogen gas is highly reactive so it can easily react with any substances or metal of the terminals and form corrosion. 

If corrosion forms on the positive terminal, then it is due to the battery overcharging. On the other hand, if the corrosion forms on the negative terminal then it is due to the battery undercharging.


Every battery has an optimal charging threshold. Sometimes the alternator overcharges the battery for some reason. As a result, the temperature and pressure inside the battery increases and the volume expands a lot. 

The electrolytes inside will then have no way other than to spill out over the battery terminals. Thus, overcharging can lead to the terminals being corroded. 

Reaction of the Copper Clamps

A bluish precipitate over the terminals will indicate the chemical reactions due to copper sulfate. Copper itself is a great conductor. However, copper sulfate can lead to corrosion very easily by reacting with the terminal materials. 

The electricity passing through a copper wire or terminal can produce copper sulfate which causes corrosion in the battery terminal. 

Battery Age

Usually, car batteries have a lifespan of five years. If the battery is too old then natural corrosion takes place which can not be fixed. The only way out of this predicament is to get a new battery.

Overfilling The Battery With Water

The battery has a certain water level marked. The water slowly decreases and so it needs to be filled up periodically just over the mark. 

While filling the battery with water, if it goes way over the maximum expected mark, the excess water will spill and create corrosion over the terminals. 

How To Fix Battery Terminal Corrosion

Now that you are aware of the causes of battery terminal corrosion, you might be wondering how exactly you can get rid of the corrosion. Here’s some effective ways that you can fix the corrosion of the battery terminal.

Using Baking Soda-water Solution

Baking soda and water solution is incredibly effective in cleaning up mild terminal corrosion. It is especially useful to treat copper sulfate corrosion. You only need a baking soda and water solution along with a brush or toothpaper. 

  • Firstly, make sure all the ignitions of the car are turned off.
  • Remove the battery terminals from the battery connections.
  • Pour the baking soda-water solution over the terminals.
  • Gently rub it with the brush or toothbrush until the corrosion is completely gone.
  • Rinse the terminal again by using only clean water.
  • Dry off the terminal well. You can use a damp cloth or towel for this.
  • Before reattaching the terminals, using grease or petroleum jelly is a good idea. It will prevent further corrosion to the terminals.

Using Carbonic Acid

Another way to clean the corrosion is to use something with carbonic acid in them. If you don’t have baking soda available, you can just simply use one of the store bought soda or coke to fix mild corrosion. 

These sodas have an adequate amount of carbonic acid in them which cleans the corrosion.

All you have to do is to pour out the soda over the corroded terminals and rub it clean with a soft sponge the same way you would with a baking soda solution.

Removing Heavy Duty Corrosion

Heavy duty corrosion can’t be removed only by scrubbing it with the solution. If the terminals are heavily corroded, remove and soak them in a container filled with the baking soda-water solution for 20 minutes. 

This will help remove even the heavy corrosion well. Clean them with water afterwards and dry them using a cloth similarly. 

Battery Terminal Corrosion Infographic

Frequently Asked Questions

1. Why do your batter terminal corrodes in the first place? 

Corrosion happens when the acid from the battery comes into contact with your battery’s metal ends of the battery. Moreover, Sulfation also takes place when lead sulfate crystals accumulate on your battery terminal. These can get your batteries to corrode. 

2. How can you prevent battery corrosion? 

To prevent corrosion, you can put any special anti-corrosion washers or even a tiny bit of dielectric grease on the posts of your battery. AMSOIL is also an ideal pick to prevent battery corrosion as it has chemical formula to prevent rusting or corrosion. 

3. Does battery corrosion mean your battery is bad? 

Corrosion on your battery’s negative terminal could mean that your battery isn’t getting enough charge, while corrosion on the positive terminal could mean that your battery is getting too much charge. So, it may not directly mean that your battery is bad. However, excessive corrosion could damage your battery and needs to be replaced. 

Bottom Line 

You should now know about battery terminal corrosion: Why it happens and how to fix it. All these issues can easily be avoided and the expense of getting new batteries or terminals by paying attention to the state of the battery terminals more. 

Taking certain preventive measures to stop the corrosion from happening can delay the natural corrosion time to a great extent. Refraining from doing any of the causes and proper maintenance of your car batteries can minimize this problem.

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William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

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Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.