What Causes Battery Terminal Corrosion?

From a traditional, no-frills sedan for a family of four to a luxury, full-loaded sports car for a weekend road tripper, motor vehicles thrive and drive on interdependency. Each automobile is composed of thousands of parts, pieces and components. They all rely on one another to function normally, particularly those that are under the hood. Given this, it's impossible to say which part of the car is the most critical of them all. They're all important.

But it's safe to say none is more important than the car battery. Without the battery and attaching battery cables, a car can't perform its primary responsibility: take occupants from Point A to Point B. It's the source that converts energy into electricity for ignition and plays a role in propelling a car forward. It also powers a car's many other, slightly less involved processes, like running the headlights, the car stereo, windshield wiper operation and more.

While batteries are designed to last for several years, naturally occurring processes can compromise battery performance and the performance of the vehicle itself. One of those processes is corrosion, or more specifically, battery terminal corrosion. Without regular maintenance, a car battery and corrosion are on a collision course: They're bound to meet eventually and cause problems. However, by applying the proper solutions and knowing what to look for, you can neutralize the effects of battery corrosion and keep your car running for longer.

But before we get into this, it's important to understand what battery terminal corrosion is and what causes it.

What is battery terminal corrosion?

Resembling baking soda in appearance, battery corrosion is a chemical reaction that forms around battery terminals when the acid within the battery itself comes into contact with the natural moisture in the air and the bare metal of the battery terminal. Lead batteries are filled with all sorts of chemicals, gasses and materials that escape from the battery over time. While the effects of their release are imperceptible in real-time, they become noticeable as the car battery gets older. As previously noted, the flaky film that forms around the positive and negative terminals has the consistency of baking soda and is often white colored as well or tinged with green or blue.

Beyond being unsightly, battery corrosion can lead to performance problems for the vehicle.

What causes battery terminal corrosion?

Just as a car battery is composed of numerous components, chemicals, materials and gasses, the same is true for battery corrosion: There are a multitude of potential contributors. In fact, when it occurs, it's likely due to more than one factor. Here are a few of of the most common contributors to terminal corrosion:


As with anything else, wear and tear takes a toll on an automobile. Generally speaking, car batteries have a life expectancy of between three and five years. Since corrosion is naturally occurring, a car battery terminal or terminals are bound to corrode if it's never checked.


It is possible to overcharge a battery should you ever leave the lights on accidentally and need a jumpstart. Aside from being dangerous, charging for too long can elevate the internal temperature of a battery to an extent that causes the electrolytes to expand. The pressure then pushes the electrolytes out of the battery, which can kickstart the corrosion process.

The proper length of time to charge a car that won't start depends on the charging source and how much energy remains in the battery (if any).

Damaged battery

Some batteries, particularly those that are lightly used, may be damaged internally. If so, battery acid may leak out of the terminals and accumulate around them. The liquid's interaction with the metal can trigger corrosion due to the electrolytes emanating from the battery.

Too much water in the battery

Water powers numerous processes, including the performance. But just as you can have too much water, a battery can have too much water. Overfilling it can not only lead to batter failure but it will lead to corrosion when it eventually leaks out of the battery vents.

Copper clamps

A battery is worthless without the clamps there to transfer energy. If the clamps are made of copper, however, the electric currents that pass through it form copper sulfate. It's this copper sulfate that can lead to car battery terminal corrosion.

Excessive exposure to harsh elements — such as sodium chloride (i.e. road salt) can also initiate terminal corrosion.

So you now know the potential causes of a corroded battery. The effects can also be wide ranging.

How can corroded battery terminals affect a car's performance?

Dim headlights

As previously noted, a battery energizes numerous automotive processes, including the headlights and taillights. If either appear dimmer than normal, it's possible that the lights themselves need replacement. But it may also be a product of corroded battery terminals.

Engine won't turn over

The most common symptom of a problematic battery is a car that won't start when you turn the ignition. This may be because the battery is too old, forgetting to turn something off or even the fault of misfiring spark plugs, but it could also be a symptom of corrosion due to the battery cables not fully connecting to the terminals. Corrosion has formed a layer that has separated them.

Car suddenly stops

Automobiles are highly reliable, but if your car suddenly loses power, it's likely a battery issue. Terminal corrosion could be what's at fault for such a scenario.

Bottom-line: Corrosion can prevent your car from receiving the energy it needs to power its various processes. If it doesn't prevent it entirely, it will decrease its overall efficiency or stymy its typically strong performance. 

How can you prevent corrosion from affecting your battery?

Since battery corrosion is naturally occurring, it's not something that can be stopped entirely. But you can neutralize it, or at the very least, control it.

Clean car batter terminals occasionally

Perhaps the best aspect of car battery corrosion is the fact that it's visible. Thus, if you see that classic baking soda look forming around the terminals (i.e. white or off-white crusty residue), simply clean it off with a cloth or wire brush along with a cleaning solution or product-specific battery terminal cleaner. Just be sure to remove battery cables first.

Apply anti-corrosion washers

You may want to speak to your mechanic or local auto shop about anti-corrosion washers. These fit around the terminals but still allow the battery cables to draw power from the battery. The washers are lined with a formula that helps to mitigate or slow corrosion formation.

Use petroleum jelly

Another potential solution is using petroleum jelly. Petroleum jelly contains neutralizing compounds that help to ward off corrosion by protecting them from moisture and liquid that forms over time and as the battery ages. You may also want to use dielectric grease. In either case, proper application requires carefully removing the battery cables.

Baking soda

Despite resembling it, applying baking soda also works as preventive. Mixing two teaspoons of it in a cup or so of water, then pouring it onto the terminals, can be an effective deterrent.

Whether you're interested in corrosion control as a business owner or in your personal needs, Auto Technology can be of assistance for your metals, equipment and other needs. Contact us today for corrosion testing innovation that our customers turn to when they require expertise that few offer. We do — and much more.

A car battery inside an automobile.