What Is Battery Terminal Corrosion?

Key Points

• Battery terminal corrosion is a common problem that can disrupt the electrical current in a vehicle's starting system.
• Corrosion on car battery terminals can be caused by overfilling the battery, leaking battery fluid, overcharging, chemical reactions with copper clamps and age.
• Cleaning battery terminal corrosion involves disconnecting the battery cables and using a stainless-steel wire brush with a mixture of baking soda and water.
• Preventive measures to avoid battery terminal corrosion include using anti-corrosive sprays, coating with petroleum jelly or dielectric grease, avoiding overcharging or undercharging and performing routine checks.
• Universal Technical Institute offers an Automotive Technology program that teaches students how to maintain and repair vehicles, including starting systems and batteries.

A functioning battery is essential to the operation of a vehicle. The battery provides the electricity needed to start a vehicle and to power other electrical components, like the windows or stereo.

Keeping your battery in good condition is important. Taking the time to perform regular checks will help you catch problems early and get them taken care of as soon as possible.

One problem to watch for is battery terminal corrosion, which can lead to the deterioration of the battery terminal materials as well as other parts of the starting system. It’s pretty easy to spot — typically, it’s a white, blue or green-tinged covering on the battery terminal, cables or posts. Corrosion on or around your battery’s surfaces can lead to increased resistance within the circuit, which can disrupt the electrical current.

Keep reading to find out more about what causes corrosion on car battery terminals, as well as steps you can take to clean and prevent it.

What Causes Corrosion on Car Battery Terminals?

There are several reasons corrosion can appear on your battery. When your battery runs, hydrogen gas gets released and is mixed with other elements, which can cause battery corrosion to build up. Some of the main causes include:

Overfull battery

Some batteries are refillable and rely on water for their operation. However, overfilling can cause the excess water to make its way out through the vents. Once water comes into contact with the battery terminals, corrosion can occur.

Leaking battery fluid

Damage to the battery can cause cracks or holes to develop that can cause battery fluid leaks. Electrolytes from the battery can then build up on the terminals and cause corrosion to form.

Overcharging

Charging a battery for too long can raise its temperature too high, causing electrolytes to expand. Pressure is formed during this process, which needs a way to escape. Electrolytes can escape through vents and cause a buildup of corrosion on the terminals.

Chemical reaction with copper clamps

Clamps made for connecting your battery to its wires are typically made from copper. If a battery is leaking sulfuric gases, it can combine with the current being sent through the clamps, causing a chemical reaction. This leads to the production of copper sulfate, which can cause battery corrosion.

Age

When it comes to a buildup of corrosion, sometimes the cause is something as simple as age. Most car batteries are designed to have a five-year life span, so seeing corroded battery terminals around this time is not uncommon.

How To Clean Battery Terminal Corrosion

If your vehicle has battery terminal corrosion, it’s important to take care of it so your battery functions properly.

Cleaning battery corrosion is a relatively simple process, though it might take some scrubbing depending on how much has built up. It’s important to disconnect the battery cables first to ensure you aren’t at risk for electric shock.

After disconnecting the cables, you should inspect them thoroughly for any peeling insulation or excess wear. Cables that are frayed or otherwise damaged can cause battery issues, so replacing damaged ones is important.

Once you’ve disconnected and inspected the cables, you can use a stainless-steel wire brush to clean the cable contacts and terminals until the corrosion is removed. Typically, you can use a mixture of baking soda and water to remove the buildup.

Battery Terminal Corrosion Prevention

There are preventive measures you can take to help avoid battery terminal corrosion. These include:

• Invest in an anti-corrosive spray: There are a number of preventative sprays and brush-on compounds that can be applied to battery terminals and posts. Remember to disconnect the battery cables before applying.
• Coat with petroleum jelly or dielectric grease: These perform much like anti-corrosive sprays but can be more affordable alternatives. Remember to disconnect the battery cables before applying these as well.
• Avoid overcharging or undercharging: If your battery is overcharging, it’s important to take your car to an automotive technician who has the ability to check for electrical faults. Undercharging can occur if the battery is not receiving enough power to return it to a full state of charge.
• Perform routine checks: Like other important car parts, your battery should be checked often. Taking the time to inspect the condition of the battery and accompanying parts can help you catch corrosion early before it gets out of control.

Corrosion on Car Battery FAQs

How do corroded battery terminals affect start-up?

Corroded battery terminals restrict the electrical current needed to power the car because they can’t make proper contact with the cable or posts, and sometimes, even starting your car by jumping will prove impossible until you clear the corrosion!  

What are the signs of battery terminal corrosion?

Signs of battery terminal corrosion include a white, green or blue deposit on or around the battery, difficulty starting the car, dim headlights or other electrical issues. Corroded battery terminals can also emit a rotten egg-like odor.

How often should I clean my car battery to prevent corrosion?

Checking and cleaning your car battery terminals once a year can prevent corrosion while extending the life of your battery. If you live in a humid area, you may want to check your battery terminals at least twice per year as they’ll be more prone to corrosion.

Train To Work on Starting Systems and More at UTI

Being able to work on your own vehicle and diagnose problems like battery terminal corrosion is one thing, but what if you could make a career out of it? In the Automotive Technology program at Universal Technical Institute (UTI), students are taught all about the maintenance and repair of import and domestic vehicles.¹

You can get hands-on training on everything from engines to starting systems, which include the battery and related components.¹⁸ After graduation, you’ll be prepared with the skills you need to pursue a career in the automotive industry.

Request more information today to find out more about the program and how you can graduate in less than a year.⁷

UTI Campuses That Offer Automotive Technician Training

• Avondale, Arizona
• Long Beach, California
• Rancho Cucamonga, California
• Sacramento, California
• Miramar, Florida
• Orlando, Florida
• Lisle, Illinois
• Bloomfield, New Jersey
• Mooresville, North Carolina
• Exton, Pennsylvania
• Austin, Texas
• Dallas/Fort Worth, Texas
• Houston, Texas