What Causes Corrosion on Battery Terminals?

When you open your hood, you might notice whitish or blue stuff on your battery terminal. So what causes corrosion on battery terminals?

Many people find it embarrassing when their car breaks down in the middle of the road. And if they don’t have jumper cables, they can end up stuck in the middle of nowhere. After using the same battery for several years, battery terminal corrosion will start to show up. You need to know what causes it and how to remedy it. [1]

Corrosion, the degradation of a material brought on by its interaction with its environment, can happen at any stage or time. Although this term is applied to all materials, metallic materials are usually the only ones experiencing it.

Additionally, corrosion processes alters a metal’s or metal alloy’s physical, chemical, and mechanical characteristics. [2]

What causes corrosion on battery terminals?


You may notice a whitish-blue, powdery substance surrounding the battery terminals. This happens only if you frequently open the hood of your car to check the oil, wiper fluid, or transmission fluid. This indicates corrosion, and it should not be disregarded.

Corrosion can be attributed to several factors. But it is essentially due to corrosive liquids or gases from the battery leaking and interacting with the metal electrodes.

Clean your battery’s terminals and wire connectors as soon as you see corrosion. If battery corrosion is allowed to grow, it may prevent the battery and the car from conducting electricity effectively. Therefore, removing the rust from the battery terminals and understanding why it occurs is crucial.

The causes of battery terminal corrosion are outlined below:

  1. Leaking Battery Fluid

The sulfuric acid and water solution in car batteries react with the lead alloy plates to produce power. Older batteries, sometimes known as non-maintenance free or refillable batteries, have removable caps.

These may be examined and refilled with distilled water if the acidic solution becomes low. However, if the battery is overfilled, a small quantity of acid may seep through the tiny vent holes on these caps.

The battery terminals will corrode if sulfuric acid that has seeped into them comes in touch with them. A significant coating of powdery corrosion can accumulate over time. Battery fluid leakage can also be brought on by overcharging. Overcharging produces heat that causes the fluid to expand and drip from the vents of the battery [3].

  1. Venting Gases

Your battery has tiny vents that allow the sulfuric gases inside to escape, even if it isn’t a rechargeable battery [4]. Corrosion may happen if these venting gases come into regular contact with the cable connections or battery terminals. You can determine whether this is the root of the battery corrosion issue. This can be done based on where your battery’s vents are and how much gas escapes via them.

  1. Old Battery

Your battery is probably gradually losing its capacity to hold a charge if it is older than five years [5]. Corrosion all around terminals is normal when batteries get to this stage. If your battery is more than five years old, and does not leak, it might need replacement.

  1. Overcharging and overfilling the battery

Your automobile battery’s terminals may corrode if the alternator is overcharging it. While revving up the running, use a multimeter to check the voltage to ensure it is not charging above 14.5 volts.

It might also result from frequently charging the car battery too vigorously. Also, the electrolyte may leak out if you overfill the automobile battery. Although not all car batteries can be overcharged, if you have one, you should check to make sure it is not overcharged. [6]

  1. Chemical Reaction in the Copper Clamps

Copper is a reliable conductor and resists corrosion well. However, copper sulfate is produced when electric currents flow via copper terminals, which causes battery terminal corrosion. Blue corrosion on a battery’s positive terminal could be copper sulfate. Since copper sulfate doesn’t conduct electricity well, starting your car will become more difficult.[7]

Is corrosion a sign of a bad battery?


Your battery might be defective due to corrosion, typically when a car sits inactive for months. When the battery and engine are not running, corrosion typically forms on the battery terminals. Therefore, you must routinely check for and remove battery corrosion if you want to extend your battery’s life and performance [8].

After a vehicle battery has been used extensively, corrosion will also show. The battery terminal ends play a simple yet crucial job.

They link the battery to the vehicle’s electrical system. Lead or other robust, highly conductive metals are used for these terminal ends. They also offer the least amount of electrical resistance.

The entire automotive electrical system is impacted by corrosion. It prevents the flow of power from the battery. As a result, problems start to arise with your car’s electrical system. The car’s engine won’t start.

The onboard computer in your car could also be having issues. Corrosion results from a direct connection between the terminals and the battery. As a result, the terminals are exposed to corrosive gases. The fumes are produced by battery acid.

Therefore, if your car battery is old enough, you should replace it [9].

Additionally, consider replacing it if it starts to leak. If the rust eats the terminals too deeply, you might need a new battery. Therefore, you should continue checking the battery terminals for signs of early corrosion. A chalky white or blue rust along the cabling or on the terminals are its telltale symptoms.

What causes corrosion on the positive battery terminal? 


If the battery’s positive terminal has corrosion, the battery might be overcharging. Depending on the metal used for the terminal ends, the substance might be white or greenish-blue.

The material is copper sulfate if it is greenish-blue. The lead within the battery reacts with the copper from the terminal clamp. If the clamps are made of aluminum, the resulting aluminum sulfate will be whiter in color. As a result, you might observe a decline in battery quality.

The positive battery terminal keeps corroding.

When the battery is working properly, it emits corrosive fumes. This is simply how battery acid functions, and it doesn’t pose an operational or safety risk unless the battery is under undue stress [10].

The battery then starts to produce larger quantities of toxic gases that are dangerous once they accumulate.

Small levels of corrosion are typical, but if you see an unusual buildup, have your charging system checked right away. The battery will become weaker and more hazardous to attempt to jump the longer the rust is allowed to continue.

The battery releases too much hydrogen gas when overcharged or undercharged. Although we advise you to exercise caution when prodding about the terminals.

You should be able to distinguish which situation by establishing whether the rusting is on the negative or positive terminal. A battery with a defective cell is one of the most frequent reasons for overcharging. Due to the battery losing voltage, the alternator overworks to compensate for the lost power.

Overcharging the battery by the alternator will continue to cause it to emit more corrosive hydrogen gas than is usual or safe. Alternator trouble could potentially be to blame.

On the other hand, a defective voltage regulator can cause your battery to undercharge. In either case, you’ll experience a detrimental rise in the production of corrosive gas. These gases will accelerate the corrosion of battery terminals and other components thereby necessitating battery repair and replacement.

What causes corrosion on the negative battery terminal? 

Corrosion is also a possibility for the negative terminal. This typically appears as a white powder. Sulfation is the term for this. This may occur if a battery is not charged sufficiently long.

Short excursions may prevent the alternator from running long enough to charge the battery fully. As a result, you might observe a decline in cranking power over time.

Dealing with battery corrosion


You can do very little to prevent corrosion if you’ve been overcharging your battery or if it’s a refillable type and you’ve overfilled it. Inspect your terminals frequently and clean them if rust is present.

Disconnect the battery cables and clean the leads and cable contacts with a steel wire brush until they are corrosion-free. After reconnecting the battery, apply anti-corrosion lubricant to the terminals and connections. [11]

It’s also a good idea to detach and remove the battery every few years. Sprinkle the platform with a rust-prevention solution if the base where the battery sits is made of metal rather than plastic. Having known the root cause of automobile battery corrosion, we must figure out a solution. The battery terminals can be cleaned using a variety of techniques listed below.

  1. Using baking soda – water solution

A carbonated water solution and a brush are required to remove copper sulfate from the terminals. Ensure the vehicle’s ignition is off first. After removing the battery terminals, use a brush to remove part of the corrosion.

Sprinkle the baking soda solution, then keep using your brush to scrub away the corrosion. Once finished, use some clean water to clean the terminals. It is wise to apply wheel-bearing oil to the connections to stop additional harm. Petroleum jelly is an option for some, but it does not last as long as grease.

  1. Use Soda

Most soft drinks consumed have some carbonic acid. Use a soft sponge to clean the residue after pouring some soda over the terminals. In the absence of a baking soda-water solution, this works well.

  1. Cleaning heavy corrosion

You must use a bicarbonate soda solution and a toothbrush to remove excessive corrosion from your battery’s connections. First, remove the battery terminals starting with the negative one. Put the baking soda solution in cups after mixing it. Each terminal should be submerged in the solution for about 20 minutes.

Clear the terminals of any corrosive substances by scrubbing. Then, make a new one by adding the soda solution. While clearing the corrosive elements, re-soak the battery terminals.

Next, the terminals should be washed with water, dried, or wiped with a wet cloth. Sandpaper can also be used to clean the terminals. Finally, reattach the terminals, starting with the positive, after applying some grease or Vaseline.

Prevent terminal corrosion



Ensuring the alternator is not overcharging the automobile battery is the greatest technique to stop corrosion of the battery terminals. You should also have a more recent automobile battery in good shape.

Sprays that are anti-corrosive do help to stop rusting. Let’s examine the few methods for preventing battery corrosion in greater detail:

  • Change the vehicle’s battery

You might need to replace your vehicle battery to stop it from being corroded. This is because a leaky car battery results in significant battery deterioration. Changing car batteries every five years is advised to keep them in good shape.

  • Compression clamps made of copper

These clamps are among the best on the market and will aid in halting further corrosion of the battery terminals. The clamps ensure that the entire clamp comes into touch with the electric current and is made of tinned copper.

  • Battery charging

One factor contributing to battery terminal corrosion is a battery that is either overcharged or undercharged. The ideal battery voltage is frequently listed in the manufacturer’s manual.

Make sure the car battery charger is not charging it too vigorously. Utilize a multimeter to check the voltage while the engine is idling. There is a problem if the alternator charges at a voltage higher than 14.5 volts.

  • Corrosion inhibitor sprays

Numerous sprays can stop terminal corrosion. If the sprays are too pricey, you can use Vaseline or oil. The battery terminals could also be protected against corrosion using coated felt pads.


An essential part of your car is the battery. When you turn the key, it helps your engine turn by supplying energy to the starter motor. Low battery levels will make starting difficult and could cause stalling when driving.

The causes of a low battery can vary, but rust isn’t always the culprit; it can also be an outdated battery. You can use soda to eliminate corrosion from your battery terminals if you find it there.

However, it is essential that you contact a qualified mechanic right away. Numerous factors could contribute to battery corrosion, and it may also be an indication of other connectivity problems with your car. It will help to have a qualified mechanic look at it to avoid more issues.