What causes car battery corrosion?

Written by roger golden
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What causes car battery corrosion?
Corroded terminals can lead to roadside repairs. (dead battery image by Katrina Miller from Fotolia.com)

Corrosion on your car battery terminals can be annoying and destructive. It reduces the current flowing from your battery, making your car harder to start, and it literally eats any paper or cloth that it comes into contact with, even indirectly. Cleaning the terminals properly will eliminate corrosion for a while, but the only way to get rid of it completely is to find the cause of the corrosion and fix the problem at the source.

Loose connections

Check the battery terminal connections. On a top post battery, make sure that the connector is tight and that it does not move when you attempt to twist it on the post. Check the connections where the battery cable attaches to the terminal connector, including making certain that the copper wires are tightly twisted. On a side post battery, be sure that the connecting bolt is fastened down tightly enough that the battery cable is held in place even when you attempt to move it about with your hand. Having a solid, tight connection is paramount to keeping your battery in top working condition and avoiding battery corrosion.

Escaping gases

One of the causes of corrosion is from gases escaping from inside the battery. A missing, cracked or loosefitting battery cap will allow the gases to seep out, where they are catalysed by contact with the lead of the battery posts and terminal connectors and become corroded. Another possible source for leaks is pinhole cracks in the battery casing, or punctures caused by repeatedly rubbing against a screw or bolt. Faulty battery caps can be repaired or replaced, but any cracks in the battery will require a battery replacement, as the holes cannot be sealed and the battery will eventually lose the capacity to start your car.

Where corrosion occurs

Where the corrosion appears on the battery terminals can help you determine the primary cause of the problem. If the corrosion seems to be concentrated where the wires attach to the battery connector, the indication is that the wires are not properly cleaned or tightened. If the corrosion appears to grow on top of the terminal of a battery, the indication is that the connector is not making a proper circuit with the battery post, and should be cleaned and tightened. Corrosion, which appears to grow toward one side of a battery connector or in other parts of the battery compartment, generally points toward the source of a tiny leak, or indicates that battery acid has been spilt or leaked into the area.

Removing corrosion

In order to remove corrosion, you should remove the connectors from the battery terminals. Mix a tbsp of baking soda into a glass of water, and pour the water onto all connecting surfaces. Use a wire brush or battery terminal tool to remove all corrosion. Lightly coat the connecting surfaces with petroleum jelly and then replace the connectors. Be sure that the battery cables are tightly twisted and fastened so that there is a metal-to-metal bond from the battery to the battery cables.

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