National Motorists Association Blog

Corrosion on battery terminals and some tips to avoid it

Have you opened the hood on your car as you’ve noticed a problem with the engine? When you did, did you see that the terminals on the battery were coated in a whitish blueish substance?

You have? This is a sign of corrosion, which is terrible for your vehicle and can lead to some problems relating to its electrical system.

Battery terminal corrosion often occurs after several years when using the same battery. It is essential to understand what causes battery terminal corrosion and how to avoid it.

We look at the causes, how to fix them and how to prevent them from happening in the future.

What Causes Corrosion on Battery Terminals?

8 common causes of battery terminal corrosion

The leading cause of corrosion is bimetal contact that occurs between lead alloys and copper.

Most often, corrosion of battery terminals is caused by hydrogen gas inside the battery that comes into contact with moisture along with minerals and salts in the air. This leads to an occurrence of a corrosive environment. Hydrogen gas is released by the battery when it is being charged.

Another reason for corrosion might be acid leaking from the battery. The acid comes into contact with the copper wires inside the battery leads.

What Causes Corrosion on the Negative Battery Terminal?

Generally, corrosion on the negative battery terminal in a vehicle results from the battery undercharging. This often occurs when the car isn’t being driven enough, so the battery cannot accept enough charge.

What Causes Corrosion on the Positive Battery Terminals?

If most of the corrosion is around the positive battery terminal, this is probably due to overcharging of the battery.

When you overcharge a battery, the sulfuric acid along with the distilled water inside it will begin to heat up. When this happens a chemical reaction takes place that ends up with a gas-forming, which will escape through vents in the battery.

Unfortunately not all the gas will be dissipated into the air, some will end up coming into contact with the positive terminal on the battery. Once the gas comes into contact with the cold metal it will turn to moisture and will lead to corrosion forming around the terminal.

Other Reasons Why Corrosion Occurs on Battery Terminals?

Corrosion of battery terminals in a car can occur at any time and for various reasons. We look at some of the main ones below.

Discharge of Battery Followed by Rapid Recharge
This often occurs when the vehicle hasn’t been used for a long time. As a result, the battery becomes flat, and to get the engine going, you need to jump start it. You then use the car’s alternator to recharge the battery rather than connecting to a battery charger.

This, in turn, leads to a lot of wear and tear on the plates that conduct energy through the battery to the engine.

Poor Battery Contacts
If the leads that connect to the terminals are loose or have become corroded can lead to corrosion of the terminals. Any loose connections mean that there will be too much resistance, making it harder for the battery to charge and discharge. This leads to it wearing out faster and causing gases to leak out.

Running Electrical Components with the Engine Turned Off
This is one of the leading reasons for the battery in your car to fail. Electrical components inside a vehicle use more amps these days. When the engine isn’t running and still has the radio on, it places a strain on the battery. Eventually, it will lead to issues revolving around charging the battery.

High Temperature
Most batteries tend to work best in temperatures of around 70 degrees Fahrenheit. When it gets too cold or warm, this can cause a fall in a battery’s performance.

Corrosion often occurs when it gets hot because the water inside the battery fluid will evaporate a lot quicker–leading to the battery grids breaking down. This problem tends to occur most frequently if the battery inside the vehicle is over three years old.

Failure to Maintain Distilled Water Levels
Most batteries for vehicles aren’t sealed, and some of the distilled water inside them can escape over time. So there will be occasions when you need to top them up with some more distilled water. This is something that many car owners do not realize has to be done as part of a vehicle’s maintenance schedule.

Bad Alternator
Your alternator could be causing the battery to overcharge slightly. When this occurs, the temperature inside the battery will go up, causing the electrolytes inside to expand, which results in more acidic gases being released through the vents. The gases then come into contact with the terminals and cause them to begin the corrosion process.

Tips on how to Remove Corrosion for a Car’s Battery Terminals

Below is our step-by-step guide to remove corrosion from the battery terminals in your car.

Before you begin work, you need to wear eye protection and nitrile gloves. Plus, wear clothes you won’t be too upset if they get ruined.

Step 1 – Mix some baking soda with water. You will use this paste to clean both the terminals and battery cables.

Step 2 – Remove the leads from the battery and dip a brush into the cleaning solution you made up earlier. A stiff brush is fine for allowing you to scrub the solution around the terminals. Also, do the same for the parts of the battery leads that connect to the terminals.

Step 3 – After giving the terminals an excellent clean, now remove any of the cleaning solution residue using clean water. Ensure that you don’t just clean around the terminals and lead contacts. Also, wash all areas around the battery to remove any corrosion. If you don’t, it can lead to damage being caused to other areas of the battery and the engine.

Step 4 – Once clean and dry, you can now reconnect the battery leads to the battery terminals. Remember to make sure that you tighten both the nut and bolts on the leads fully.

How to Prevent Battery Terminals from Corroding

3 Tips to prevent battery terminals from corroding

There are a few things you can do that will help to reduce the risk of the battery terminals corroding.

There are specialist coatings such as CRC Battery Terminal Protector that you can spray onto the terminals that will help to prevent this problem from occurring.

You can also fit onto the terminal felt washers that have been treated with a solution to reduce the risk of them rusting.

Finally, you can buy certain types of grease that you can apply to the terminals before connecting the battery leads to them.

The main objective is to prevent any acid, hydrogen gasses, or oxygen from coming into contact with all of these. These can eventually lead to the terminals on your car’s battery corroding.

Important Tip

The best way to prevent the battery terminals from corroding is to ensure that it goes under 12 volts as this will help them to remain clean. Doing this you will never have to clean or apply any grease to them.

We hope you’ve found this article helpful, and it will prevent you from having to spend money on replacing your battery too soon in the future.

I’m Tim Miller, an auto mechanic and the Editor-in-chief at batteryglobe.com. I love writing to share my experiences and expertise. Many articles about car batteries and accessories can be found on my website. Get connected with me on Facebook and Twitter.