Corroded battery terminals can prevent your vehicle from starting. You could have so much corrosion around your battery connections that the resistance is stopping the current from getting through to start your vehicle.
Battery corrosion is caused by hydrogen gas being released through the battery vents from the acid inside the battery. This mixture builds up over time and is the white, green, or blue tinted corrosion we see on battery terminals or cables.
Most often the corrosion occurs on the negative battery terminal, which is a sign of undercharging the vehicle’s battery. This typically happens when the alternator does not have enough time to replenish the lost battery capacity. Battery corrosion on the positive terminal is normally from overcharging. If this is what you are seeing in your vehicle, it may be best to have your alternator checked for proper output.
Once corrosion occurs, if the buildup is not too severe, the terminals can be cleaned by using a battery cleaner with sandpaper or a wire brush to loosen up the corrosion and scrub it away. Before doing this, you should turn your vehicle off and disconnect the battery cables from the vehicle. For safety the negative cable should be disconnected first, and hooked up last. A solution of warm water and baking soda will neutralize any acid on top of the battery or in the vehicle tray.
Sometimes, a corroded battery cannot be sufficiently cleaned, and it is time for a replacement. When inspecting your battery, be sure to check the condition of the case itself. If it is leaking or swollen, it is time to replace the battery instead of cleaning the corroded terminals and cables.
The best way to fight corrosion is to prevent it from ever starting. You can use a spray battery protector which is meant to prevent corrosion build-up on battery terminals and cables. Always start with a cleaned-up connection and read the manufacturer’s directions before use.