Rick's Free Auto Repair Advice

Does corrosion on car battery terminals mean the battery is bad

Does corrosion on car battery terminals mean the battery is bad

Corrosion on car battery terminals does not necessarily mean the battery itself is bad, but it does indicate an issue that needs to be addressed. Corrosion can occur for a number of reasons:

Electrolyte Leakage Causes Battery Terminal Corrosion

Sometimes the battery can leak acid if there’s a gap between the plastic battery case and the battery post. The acid can cause corrosion on the terminals.

battery terminal corrosion

Hydrogen Gas During Charging Can Cause Corrosion of Battery Terminals

Batteries can release small amounts of hydrogen gas during charging, which can react with other substances in the environment to create corrosion.

Dissimilar Metals React in the Presence of Moisture to Form Galvanic Corrosion

The reaction between dissimilar metals (like the copper in the cable and the lead in the terminal) can lead to corrosion. Living in a humid or coastal area can accelerate the rate of corrosion due to the presence of moisture and salt in the air.

Battery terminal corrosion can cause battery failure

Corroded battery terminals create electrical resistance, making it harder for current to flow. This can hinder proper battery charging and even reduce the amount of current available to start your engine and run all the electrical accessories.

Leaking battery acid can damage other components

If the corrosion is due to a leaking battery, it might not just damage the terminals. Acid can corrode other nearby components or the battery tray.

What to do if you find battery terminal corrosion

Tools and supplies you need to clean battery terminals and posts

Battery brush

battery terminal brush

Remove the battery cable terminals and clean the inside of the terminal and the battery post with a battery cleaning brush

10mm socket and ratchet or 10mm wrench
Protective eye wear and rubber gloves
Baking soda

• Wear protective gloves and safety goggles.
• Disconnect the negative battery terminal. Then disconnect the positive battery terminal
• Use a wire battery brush to clean corrosion off the inside and outside of each terminal and battery post
• Use a rag to wipe off all dirt and corrosion from the top of the battery. Use a mixture of baking soda and hot water to neutralize the battery acid and remove any remaining buildup. Rinse with a wet rag. Discard the rag
• Reconnect the positive battery terminal. Reconnect the negative battery terminal last
• Apply a thin layer of petroleum jelly or a specialized terminal protector to the terminals. This helps prevent future corrosion.
• After cleaning the corrosion, if you still have issues with your vehicle (e.g., it doesn’t start easily, the lights dim, etc.), then you might need to test the battery or have it tested at an automotive shop to determine its health.

©, 2023 Rick Muscoplat

Posted on by Rick Muscoplat


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