These caps have tiny vent holes through which small amounts of acid can leak if the battery is overfilled. If leaked sulfuric acid in the battery fluid touches the battery terminals or cable contacts, it will cause them to corrode. If it goes on long enough, a large deposit of powdery corrosion can build up.
Will vinegar remove car battery corrosion?
If you find yourself dealing with extra stubborn corrosion that doesn’t come off with just baking soda, try the baking soda and vinegar method to clean your battery terminals. Vinegar is a powerful acid which can break down corrosion pretty quickly when combined with the fizzing action of the baking soda.
How do you clean corrosion off AA batteries?
The best way to remove alkaline leakage from the device is to neutralize by carefully dabbing with a few drops of a mild acid like white vinegar or lemon juice. For stubborn leaks, an old toothbrush dipped in vinegar or lemon juice gets the job done.