Battery Terminal Corrosion Causes (How to Fix & Prevent It)

Battery terminal corrosion is bad for your car and can create issues with the electrical system. Here's what causes it and how to prevent it in the future.

Battery Terminal Corrosion Causes

You have probably encountered a whiteish and blue substance on your battery terminal when you are opening your hood.

The car’s battery is vital for the smooth operation of your car. It controls electric consumers like ignition, headlights, listening to the radio, or operating the AC.

Having a car stall in the middle of the road can be embarrassing for many, and if you do not have jumper cables, you may find yourself stranded in the middle of nowhere.

Battery terminal corrosion will appear after years of driving with the same battery, and you need to understand what causes it and how to fix it.

5 Causes of Battery Terminal Corrosion

The most common cause of battery terminal corrosion is hydrogen or electrolyte leakage from the battery. It can also be caused by an alternator slightly overcharging the car battery over a long period of time. Chemical reactions with copper clamps are not rare either.

These are the few different reasons why you may notice corrosion on your battery terminals.

Here is a more detailed list of the 5 most common causes of battery terminal corrosion.

1. Hydrogen gas leakage

Leaking Car Battery

The battery turns acid into an electric current. There are moments that the hydrogen gas in the battery leaks and finds its way into the atmosphere. It reacts with other substances, and you get battery terminal corrosion.

Depending on which side it forms, you can diagnose various battery problems. If it is on the negative terminal, this is a sign of undercharging, while if it is on the positive terminal, it is due to overcharging.

2. Electrolyte leakage

This problem is synonymous with lead-acid batteries. Due to age or damage, the battery’s electrolyte can leak and accumulate on the battery terminals. The probability of the electrolyte leaking is increased if you overfill the battery water.

3. Chemical Reaction In The Copper Clamps

Copper is a good conductor and does not corrode easily. However, when electric currents pass through the copper terminals, there is the production of copper sulfate, which leads to battery terminal corrosion.

A bluish precipitate on the copper terminals can signify copper sulfate. Copper sulfate does not conduct electricity well, and that is why you will start experiencing trouble starting your car.

4. Overcharging

If your alternator is slightly overcharging your car battery, it might cause corrosion on your car battery terminals. Check your voltage with a multimeter when your car runs to make sure it is not charging over 14.5 volts when you are revving the engine.

It can also be because you are frequently charging your car battery with a car battery charger too hard.

5. Overfilling the battery

Refill Car Battery

If you overfill your car battery, it might cause the electrolyte to leak out, as mentioned before. Not all car batteries are refillable, but you should absolutely double-check if you have one so it is not overfilled.

How to Fix battery terminal corrosion

Car Battery Terminal Corrosion

Now, when we know what causes the car battery corrosion, we need to know how to fix it. There are some different methods you can use to clean the battery terminals.

1. Baking soda – water solution

If you want to remove copper sulfate from the terminals, you will need some baking soda water solution and a brush. First, ensure that the car’s ignition has been turned off. Remove the battery terminals and use your brush to remove some of the corrosion.

Pour the baking soda solution and continue removing the corrosion with your brush. Once done, clean the terminals with some clean water. It is prudent to smear some wheel bearing grease on the terminals to prevent further damage. Some people may opt for petroleum jelly, but this does not last as long as grease.

2. Soda

Most of the soft drinks that we take have some carbonic acid in them. Pour some of the soda on the terminals and use a soft sponge to remove the residue. This works well in the absence of a baking soda-water solution.

3. Cleaning heavy corrosion

If your battery has excessive corrosion on the terminals, you will need to use a baking soda-water solution and an old toothbrush. Start by removing the battery terminals – the negative should be first. Mix your baking soda solution and place it in cups. Soak each of the terminals in the solution and let it soak for the next 20 minutes.

Scrub off the corrosive materials on the terminals. Pour in the soda solution and make a fresh one. Soak the battery terminals again while removing the corrosive materials. Clean the terminals with water and let them dry or wipe with a damp cloth. You can also use sandpaper to clean the terminals. Apply some grease or Vaseline and reattach the terminals – start with positive.

How to Prevent Battery Corrosion

Corrosion Car Battery

The best way to prevent battery terminal corrosion is to make sure the alternator is not overcharging the car battery. You do also want to have a newer car battery in good condition. Anti-corrosive sprays do also work to prevent corrosion.

Let’s take a little more detailed look over the few ways to prevent battery corrosion:

1. Replace the car battery

Because a leaking car battery causes a lot of battery corrosion, you may need to replace your car battery to prevent it from happening again soon.

Car Batteries are anyways recommended to replace every 5 years always to keep them in good condition.

2. Copper compression terminals

These clamps are one of the best in the market and will help prevent further battery terminal corrosion. The clamps are made from tinned copper and ensure that the whole clamp comes into contact with the electric current.

3. Battery charging

One of the causes of battery terminal corrosion is a battery that is overcharged or undercharged. The manufacturer’s manual often has the recommended battery voltage. Make sure you are not charging it too hard with your car battery charger.

Also, check the voltage when the car is revving on idle with a multimeter. If the alternator is charging over 14.5 volts, there is something wrong with it.

4. Anti-corrosive sprays

Various sprays are available on the market to prevent terminal corrosion. You can also use Vaseline or grease if you find the sprays expensive. Coated felt pads could also be used to prevent corrosion of the battery terminals.

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Category: Electric
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Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.