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What Causes Car Battery Corrosion and How Do I Clean It?


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Your car battery is extremely important allows your vehicle to start and function. Battery corrosion or acid leakage is a sign of a failing battery. Battery terminals, posts, and even cables will display a fuzzy, gritty white, blue, or green substance.

Why Does Corrosion Form on Car Batteries?

If your battery is suffering from corrosion at the posts preventing it from charging, you may be five minutes and a little baking soda away from starting your engine. But what is all that corrosion around the battery post?

Corrosion is a product of chemical reactions inside and outside of the battery. While batteries warm up from charging, a small amount sulfuric acid, known as battery acid, leaks from the vents of the battery. When it comes in contact with the lead posts, it reacts to form corrosion. Also, the contact between different metals in the battery post and battery terminals can form corrosion as well.

If the corrosion is purely white with a grainy or powdery texture, the battery could have missed a few cleanings, the posts were not protected from corrosion, or the battery may be leaking. When the corrosion is purely white, the battery is less likely to remain serviceable. However, if you notice a blue, green, or rust colored substance, the issue is likely that the battery terminals or battery posts have not been serviced, are not protected, or the terminals need to be replaced. If there is a color other than white around the battery terminals and posts, the battery posts may be eroded, and the terminals may break during removal.

Cost and Upkeep of a Car Battery

According to RepairPal, the average battery will run between $149 to $202 on average (including a quality battery and professional installation). We recommend a high-quality battery to ensure a longer life and a safer replacement for the more computerized vehicles on the road. You should keep your battery in good shape and inspect it often to ensure a full life.

Maintaining a battery need not be a daunting task, and battery maintenance can be performed at home on many vehicles. Many late-model vehicles have batteries stored in odd places, which may be hard to access or even find. Use your owner's manual to locate the battery, and if you do not feel comfortable servicing the battery yourself, the cost of servicing the battery is typically negligible.

Most car batteries are sealed, so there are only five maintenance checks that must be completed.

  • Remove and clean the terminals and battery posts
  • Verify presence and cleanliness of battery retaining hardware, cold weather insulation, and that the battery tray is free of corrosion
  • Apply the manufacturer suggested grease to protect the battery post, and re-install the terminals
  • Ensure a protective coating is sprayed or brushed onto all exposed metal on the battery
  • Check the voltage of the battery, and ensure proper operation

How do I clean corrosion from my car's battery?

It is recommended in your owner's manual how often the battery terminals should be inspected, but keep in mind any time the battery seems low that corrosion may be the issue. This is extremely common and has led to many needless battery changes. The best part, battery terminal exterior corrosion is something a simple cleaning can address.

Here's how to clean your car's battery:

  1. Safety first! Remember to wear gloves and goggles.
  2. Be sure to check your user manual before disconnecting the battery. Some vehicles may need a code to re-access the radio, etc. Make sure you have these things nearby before disconnecting!
  3. Carefully disconnect the battery, negative first and then positive (normally marked by a cap or red color), making sure no metallic items are connecting a battery terminal to anything else. Especially the other battery terminal.
  4. Mix a solution of hot water with baking soda to build the consistency of a paste. This will neutralize the low Ph of battery acid, and penetrate the built-up corrosion for complete removal.
  5. Dip a toothbrush in the solution and scrub the battery posts, inside the battery terminals, and anywhere which may be covered in white corrosion. Take a moment to clean and inspect the entire battery as well, rinsing with water and drying with a clean cloth when needed.
  6. Apply a manufacturer grease (or petroleum jelly, or vaseline) to the inside of the cable ends.
  7. Reattach the battery terminals tightly to their respective posts (try wiggling them to make sure they're secure) and start the car to test. Do not touch or attach the incorrect cable to the incorrect terminal! This can result in massive electrical damage to your vehicle!

If the battery is still not performing properly, have it tested and replace as necessary. 

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