Rick's Free Auto Repair Advice

What causes car battery corrosion?

Car battery corrosion causes

Car battery corrosion is caused by leaking sulfuric acid, and battery sulfation caused by battery undercharging or being in a constant state of discharge.

Liquid Sulfuric acid leak and sulfuric acid vapor leak

As a car battery discharges and recharges or heats and cools. That causes the battery acid to expand and contract and vaporize. Maintenance free batteries retain acid vapor and water so it condenses and return to the cells. That’s why you never have to add water to a maintenance free battery. However, as the plastic battery case ages, some of the acid and acid vapor can leak out of the case around the battery posts. When sulfuric acid or vapor interacts with moisture in the air, it causes powdery substance on the posts, terminals and cable. The corrosion can be either a white or blue powder.

Blue/green car battery corrosion

Blue/green powdery corrosion is anhydrous copper sulfate and it forms on copper battery cables and terminals that contain copper. This type of car battery corrosion causes increased resistance that interferes with engine cranking and proper battery recharging. It can also lead to transient current flow (battery drain) even when you’re engine isn’t running.

White car battery corrosion

White car battery corrosion usually forms on the negative battery post and terminal and can be a symptom of undercharging or a discharged battery. This condition is caused by a failing alternator or short trips when the alternator doesn’t run long enough to replace the used battery power.

When car battery corrosion returns after cleaning

If you’ve cleaned the battery terminals using the procedure shown here but the corrosion returns quickly, that’s the sign of a leak between the plastic case and the battery posts. The only fix is a new battery. You cannot reseal these areas.

©, 2020 Rick Muscoplat

Posted on by Rick Muscoplat


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