why does my battery terminals keep corroding

Corrosion on the terminals is due to hydrogen gas being released from the acid in the battery. It mixes with other things in the atmosphere under the hood and produces the corrosion you see on the terminals. Generally, if the corrosion is occurring on the negative terminal, your system is probably undercharging. If on the positive side, it is probably overcharging. Most often it will be seen on the negative side because the battery is usually in an undercharged situation. This is just the nature of the beast, I'm afraid. You will need to thoroughly clean the corrosion from off the posts. You can use baking soda and water solution to help in this endeavor. Ensure you have eye protection, clothes which you don't care if it possibly gets ruined (acid can do nasty things), and some type of gloves (nitrile gloves work great).


Clean the area using the solution and a brush. It doesn't have to be a steel bristle one, just one which is stiff enough to remove the gunk. You will have to remove the battery cables to get them completely clean (sorry about the radio channel presets! ). Finish your clean up with a good dose of water to flush the area of any residual corrosion. If you don't, it can eat away the paint in the nearby areas. When done cleaning, to help slow down the corrosion process, coat the terminals with grease (high pressure grease or wheel bearing grease works as good as anything). It doesn't have to be a lot, but ensure total coverage of the metal at the terminals. Cover the outside of the terminals
after you have put the cables back onto your battery. You can also purchase a aerosol spray coating which you can purchase from your local parts store.


Your main objective is to keep the lead, escaped hydrogen gas, and oxygen from mixing which forms the corrosion you see after a period of time. Over time the grease will break down and corrosion may start, so regular cleaning and reapplication is a must. If you do this about every six months, you should be in good shape. Acid Corrosion в Causes and Cures. Have you ever lifted your hood and found corrosion on your battery terminals? Yuck! Not only is it unsightly, but corrosion build up can also build up between your terminals and wires в causing hard starts and dead batteries. (fig. 1) What causes this build up? As you know from our Anatomy of a Battery article, automotive batteries are filled with sulfuric acid. (fig. 2) As your battery heats and cools with your motor, hydrogen gasses are released from the battery through the vents in the battery. (fig. 3) These gasses mix with other particulates around the battery.


That mixing produces corrosion which forms on electrical connections в which is why we find it on our battery terminals. How can we get rid of corrosion? Thereвs no easy way to get rid of the corrosion в it just needs a good cleaning. To get those terminals clean, there are a couple of avenues you can follow. Ideally, youвll have a wire brush (fig. 4) handy and some battery cleaner. (fig. 5) If these arenвt available to you, some baking soda mixed with a little water will take the place of battery cleaner, and a toothbrush works in place of a wire brush. Just be prepared to scrub a little harder! How can we prevent corrosion? There are multiple ways to prevent corrosion from building up on your battery terminals.


These solutions should always be applied to freshly cleaned or new batteries! Use a spray battery protector. This applies a protective layer to the terminals and connectors. (fig. 6) Apply an anti-corrosion gel to your terminals before connecting the battery cables. This may not protect the rest of the connector, but corrosion wonвt build on the terminal. So no more worries about hard starts. (fig. 7) Use felt terminal protectors. These are impregnated with a corrosion inhibitor. Theyвre fairly popular because they prevent corrosion without the mess of sprays or gels. (fig. 8) Next time you get stuck replacing the battery in your car or truck, consider implementing these preventative measures to stop corrosion before it becomes a problem. Thanks to Becky C. for the question!

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