Why Do Car Batteries Corrode? Understanding the Culprits

As many of us know, our car batteries are an essential element of our vehicles, giving our cars the electrical power needed to start our engines and help run the vast and varied electrical systems found in modern cars.

One common issue we see all the time here at Allstar Batteries is corrosion on car battery terminals. If your car battery has corrosion on it, this can cause a range of problems, from poor electrical connections to complete battery failure. If you’ve found yourself stranded in your driveway with a car that won’t start, checking your battery for corrosion is one of the first steps you can take to make sure everything is working the way it should be.

Let’s delve into why your car battery may have corrosion issues and some ways to prevent and manage it.

What’s the science behind battery corrosion?

Battery corrosion happens mainly at the battery terminals, where your battery cables connect to the battery posts. Corrosion is a chemical reaction that takes place between the sulfuric acid inside the battery and the metal conductors of the battery terminals. When this reaction happens, it generates hydrogen gas. When that gas is exposed to air, it forms a white, powdery substance known as lead sulphate.

What are some common causes of car battery corrosion?

Overcharging or undercharging your car

One of the main causes of battery corrosion in cars is improper charging. Overcharging your battery can cause an excess of heat, which speeds up the chemical reactions responsible for causing corrosion on your battery. Conversely, undercharging your battery can lead to the accumulation of lead sulphate on the battery plates, increasing the chances of corrosion.

Some of the things that can lead to over or undercharging your car battery are:-

  • Leaving your lights on
  • Taking lots of short trips
  • Driving your vehicle infrequently
  • Using a lot of electronics whilst idling for long periods
  • A fault in charging systems (eg. malfunctioning alternator or voltage regulator)
  • Installing aftermarket electronics
  • Damaged or old batteries
  • Ignoring warning lights in your dash
  • Not jump-starting a vehicle properly
  • Using an incorrect charger for your battery

Battery leaks and spills

When battery acid leaks or spills, it can expose the battery terminals to the corrosive sulfuric acid in the battery, leading to corrosion. This usually happens due to damaged battery cases or improper handling of the battery.

Some of the things that can lead to your car battery having leaks or spills are:-

  • Overcharging the battery
  • Old batteries
  • Wear and tear
  • Overfilling the cells with electrolyte
  • Damage, such as cracks or dents in the casing
  • Excessive heat in the engine bay
  • Extreme temperatures
  • Frequent and severe vibrations

High temperatures

Often, extreme heat can increase the rate of chemical reactions within the battery, leading to faster corrosion. For example, storing your car in temperatures above roughly 38 degrees for extended periods can help accelerate corrosion on the battery.

Environmental factors (in other words, Brisbane summers)

We all know that Brisbane is hot and humid in summer. When moisture combines with lead sulphate, it forms a conductive solution that can cause leakage and corrosion in your battery.

Low-quality battery terminals

Poor-quality battery terminals from cheap, inferior batteries are more prone to corrosion. Investing in high-quality, corrosion-resistant terminals is the way to go. (You won’t have to worry about cheap and nasty batteries if you get a battery from Allstar Batteries.)

Loose or dirty connections

We’re not talking about your underbelly mates here. We’re talking about loose or dirty battery connections that can lead to resistance in the electrical charge from your battery, causing it to work harder and generate more heat.

Old batteries

As car batteries get into their old age (usually over 5-7 years old), they become more susceptible to corrosion. Regular maintenance of your battery and timely replacement can help prevent this.

Car battery corrosion can be a pain in the bum to deal with, but with proper maintenance and an understanding of the underlying causes, you can keep it in check.

If you look under the hood and find you have corrosion on your battery, you may want to read our article What to do if your car battery is corroded to give you some hints and tips on how to deal with it.

If you try everything in the above article and your battery still isn’t working, make sure you talk to us today about getting a replacement battery for your vehicle.

We have the northside of Brisbane covered when it comes to your battery requirements so drop into one of our main stores at Brendale, Caboolture or North Lakes.


12 Garret Street
Brendale Qld 4500
Ph: 0413 692 236


6/106 Lear Jet Drive
Caboolture Qld 4510
Ph: (07) 5309 4905


12/88 Flinders Pde
North Lakes Qld 4509
Ph: (07) 3048 2293


Allstar Batteries - 'Positively the Best'