Why Do Car Batteries Corrode and How to Prevent it? Ask Alex #3

This site contains affiliate links to products. We may receive a commission for purchases made through these links.

Hey guys!

This week I want to aswer Kevin’s question back on the post where I reviewed my favorite car batteries.

Kevin asked: Why do car batteries corrode?

So i’m going to dive right into it to help you find out why this happens, what’s the effect it may have in your car’s functioning and how to get rid of corrosion!

The reason SOME car batteries corrode

I’m sure you’ve seen this before:

corroded battery terminal

Corrosion (this blue-ish dust) on the battery’s terminals happens only on lead-acid batteries, and it is caused by the hydrogen gas that acid releases when it reaches certain temperatures.

It mixes with other components from the atmosphere and it attacks the metal terminals from the battery as they are exposed to air.

When does this happen?

As a rule of thumb, you’ll find corrosion on the negative terminal of the battery if this is under low charge and it will appear on the positive (red) terminal if the battery is being overcharged.

We’ll typically find corrosion on the negative terminal as batteries are usually being undercharged. Which by the way is a good way to spot a malfunctioning alternator’s regulator (corrosion on the right terminal)

Negative effects of corroded terminals

Corroded materials do not have the same electrical properties as their non-corroded versions.

A layer of corroded lead will have an impact on the amount of power that the battery can deliver as it encounters an initial resistance.

This is typically one of the first things to check when the engine has cranking issues.

How to clean the terminals from corrosion

I have good news:

It’s very easy to clean the terminals and prevent further corrosion to happen.

Here’s what you have to do.

  1. Get some baking soda and dillute it on water.
  2. Get a metal brush, a pair of gloves and make sure to wear eye protection of some kind.
  3. Making sure that the key is off the ignition, take the negative terminal off first, then the positive one. (You may lose the radio channel presets on old models)
  4. Thoroughly clean each terminal using the brush and soda solution.
  5. Clean up the area of any remaining corrosion with water and a piece of cloth/paper. (This kind of corrosion may eat your car’s paint so make sure to clean the rests!)
  6. To prevent further corrosion from happening, give the terminals a coat of vaseline (or some spare wheel bearing grase you may have laying around) 
  7. Each six months get the hood up and check, as the grease may break down and corrosion could start building up again. Re-apply and you’ll be fine!

Wrapping Up

So as you’ve seen, solving this corrosion issue is really easy.

However, I’m sure you noticed I said “SOME” batteries…

AGM batteries and other kind of batteries don’t suffer from this issue. 

Consider it when purchasing your next car battery!

If you have any questions, hit me with them on the comment section below!