White Powder on Car Battery Terminals: Here’s What It Is

A very common occurrence with lead-acid batteries is corrosion. This corrosion is due to the interaction of lead sulfate and the lead in the terminal of your car battery. This corrosion causes a white substance to build up around the terminals. This chemical reaction is not something to do away with, as the plates are continuously reactive. However, there are ways you can minimize lead shedding.  

In a case where the positive terminal is corroded, it is a result of electrolysis due to the type of alloys used to make the cable connectors and battery terminals. This corrosion is also caused due to the emission of hydrogen gas from the acid in the electrolyte. This is when the white substance coats the terminal. If the coating is on the top of the battery, or the terminal posts, then it could be because of a damaged seal caused by overcharging or an old battery. 

What Causes the White Powder on Car Battery Terminals?

The white powdery substance on your car battery terminal is usually zinc sulfate and lead crystals. You would see a white or bluish powdery substance for corroded copper connectors, while aluminum connectors are corroded with aluminum sulfate.

White Powder on Car Battery Terminals: Here's What It Is

Other causes of corrosion include thermal expansion, lack of ventilation, and overcharging. 

Thermal expansion is due to filling the electrolyte with too much water. Due to the high amount of water in the electrolyte, heat will make the water expand and push the mixture out of the vents on top of the car battery. This spilled liquid then interacts chemically with the metal in the battery terminals, causing it to rust.

Acid fumes buildup due to a lack of ventilation and interact with the exposed metal parts of the battery. The electrolyte can also flow into the case and interact with the lead and other metals. 

Overcharging is another reason for corrosion, especially in sealed lead-acid batteries such as AGM (Absorbent Glass Mat) batteries. Traditional flooded wet-cell batteries cope better with overcharging compared to newer battery models. 

Does This White Powder Affect the Battery’s Function? 

Corrosion, as a usual occurrence, may not affect the car battery in small quantities; however, a relatively large amount of buildup can cause some damage to the battery. It can cause hard starts, or worse still, the car not starting at all. The car would also have problems getting sufficient power and the electrical components, such as the air conditioning, cabin light, or radio. 

Your car’s onboard computer can also be affected. The onboard computer prevents problems by warning you and gathering important information from the sensors to keep the car operating. A malfunctioning onboard computer is risky for you and your vehicle regarding safety. 

Corrosion on the negative plates, called sulfation, can cause the car battery to die before it normally should. 

How To Avoid Car Battery Corrosion 

Here are ways you can prevent or minimize corrosion in your car battery; 

  • Grease coating: Using battery protective grease, rust inhibitor spray, or petroleum jelly around the battery terminals is a good way to prevent rusting. It is best to use silicon-based grease such as battery grease, as it lasts longer than petroleum jelly. 
  • Use terminal protectors: Battery terminal protectors such as felt battery washers are a good way to protect your battery terminal from corroding. These washers work by absorbing the vapor emitted at the battery post. They last for several years and keep the terminal clean. Note that you still need to grease the top of the washers and the battery terminal before installing. 
  • Ensure the temperature is not extreme: High or too low temperatures can affect your car battery’s ability to hold a charge, resulting in undercharging. To minimize corrosion in this case, make use of a charger with a wide range of float voltages and set it to ambient temperature. When the surrounding temperature hits 29 degrees, reduce the float charge, and increase it when the surrounding temperature falls below. 
  • Using copper compression terminals: the clamps made from tinned copper ensure that the entire clamp comes in contact with the battery cable to distribute the electric current uniformly, thus preventing corrosion. 
  • Control charging: An overcharged or undercharged car battery can lead to corrosion or overall damage as time goes on. Ensure you are not charging your car battery more than is required. The manufacturer’s manual contains information on the correct battery voltage required. You can check the voltage with a multimeter while the car is revving on idle mode. If the alternator is charging over 14.5 volts, that indicates a problem. Overcharging can induce the release of excessive hydrogen gas, causing corrosion to build up on the battery’s metal parts. Asides from corrosion, charging issues can concern more than just the battery. 
old car battery

How To Get Rid Of The White Substance 

Removing the white gunk around your car battery terminal is easy. Here are a few steps to getting your car battery clean in no time;

  • What you need: you would need a cleaning solution, a wire brush or battery brush, pliers, and a clean rag. It is also advised to use safety gear such as gloves and goggles. Also, ensure that you wear clothing you would not mind getting stained. 
  • Disconnect the battery cables:  to avoid electric shocks; you need to remove the battery cables. Detach the negative cable first from the negative terminal. The negative cable is usually marked black. Then detach the positive cable, usually marked red, from the positive terminal. If you find it difficult to remove the cables, do not force it. Instead, apply the terminal cleaner and let it sit for some minutes to loosen it up. 
  • Apply the cleaning solution:  there are different types of cleaning solutions for battery terminals, including the DIY mixture of baking soda and water. For the baking soda plus water method, mix a tablespoon of baking soda with a cup of water, then use a wire brush or battery brush to scrub the corroded area with the mixture. Alternatively, you can coat the terminal in baking soda, add a little water, then scrub. Battery terminal cleaners are also a more expensive but effective option for removing corrosion. They usually come in spray form and are recommended for heavily corroded terminals. However, you have to be extra careful with battery terminal cleaners, so it does not cause a strain on your paint job. 
  • Rinse and dry: After giving the terminals a good scrub, rinse them with clean water and let them air dry. For faster drying, you can wipe it with a clean rag. Once the terminals are dry, apply some grease to them to prevent further corrosion. 
  • Reconnect the battery: Following the reverse order from disconnecting the battery, attach the positive cable to the positive terminal first and then the negative cable to the negative terminal. Tighten the connection using pliers or a wrench, as loose connections can inhibit charge transfer between the battery and the engine. 

Final Thoughts

The white debris around your car battery is usually not something to worry about. However, if left to buildup can affect the proper functioning of your car and its electrical components. Routine checks can help prevent this buildup and keep your car battery clean.

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