Have you ever noticed a white, crusty substance on your batteries and wondered if it poses a risk? Whether you’re dealing with lead-acid batteries in your car or alkaline batteries in your portable devices, understanding the origins and dangers of this white, crusty substance is crucial for keeping yourself and your equipment safe.

The white crusty stuff on batteries can be dangerous in traditional wet cell (lead-acid) batteries, commonly used for starting cars and powering other heavy-duty equipment. However, it is not harmful if found on an alkaline (dry-cell) battery in portable devices such as laptops.

In this article, I’ll talk about the white substance that forms on lead acid (wet cell) and dry cell (alkaline) batteries. I’ll look into its causes in both battery types and examine its effect on battery health as well as your safety. Read on to learn more about this mysterious crusty stuff.

What Is the White Crusty Stuff on Your Battery?

The white crusty stuff on your battery is a type of build-up that can be caused by corrosion, sulfation, oxidation, and many other processes. Your battery type plays a key role in the formation of this build-up.

Potassium Carbonate Build-Up on Alkaline Batteries

Alkaline batteries are typically “dry cells” and do not rely on a liquid electrolyte. Instead, they employ a liquid potassium hydroxide solution that is absorbed into the reactive elements. As a result, there is no free-flowing liquid present. The reactive elements in this type of battery include manganese dioxide and zinc metal.

The white, crusty substance that may appear on this type of battery is potassium carbonate, formed when the potassium hydroxide from the battery leaks and reacts with carbon dioxide in the air. Potassium carbonate is dangerous if ingested and can potentially cause skin irritation or burns.

You thus need to be careful when dealing with corroded battery terminals.

What Causes Leaks in Alkaline Batteries?

You may wonder how a properly encased alkaline battery can leak. The answer is relatively straightforward: pressure build-up.

Side reactions within the battery generate hydrogen gas, which then increases in pressure and, upon venting, carries some of the electrolytes out of the battery. This electrolyte then reacts with oxygen in the air, forming the characteristic white, crusty substance.

Lead Crystals and Sulfate Deposits on Lead-Acid Batteries

Traditionally known as wet-cell batteries, lead-acid batteries are frequently used to start automobiles. The white, crusty substance on them is likely to be lead crystals, lead sulfate, and zinc sulfate. These substances are potentially dangerous and have been classified as probable carcinogens for human beings.

The formation of these substances results from corrosion, which is caused by the interaction between sulfate ions within the battery and the lead present in the battery terminals. There is always a likelihood that a certain amount of electrolyte may seep through the seals where the terminals pass through the casing, thereby reacting with the battery terminal.

When lead plates within the battery are constantly exposed to sulfuric acid, lead crystals can form and potentially leak out through damaged vents and seals. It can also result in the build-up of large deposits of white material on the surface of the battery, particularly in older batteries where leaks may occur due to age and corrosion caused by sulfuric acid.

Zinc sulfate deposits, on the other hand, are primarily a result of the utilization of zinc additives in batteries. Both of these substances are of a whitish hue and can be challenging to distinguish from one another.

What Causes Corrosion in Lead-Acid Batteries?

Corrosion in lead-acid batteries is unavoidable since the lead plates in the sulfuric acid medium are continuously reactive. The corrosion rate increases with battery age since the lead in the plates and battery terminal posts begins to soften and shed with continued exposure to the acid.

So when you persistently notice that white crusty substance on your battery, it is time to consider a replacement.

At other times, a faulty battery vent cap can leak sulfuric acid into the battery surface. This acid will react with the lead terminal post and again form white balls, which are lead sulfate.

Thermal expansion due to overfilling the battery or overcharging is the main trigger of this type of corrosion. The balls can form around the terminal post or spread around the battery surface, depending on the leakage point.

However, corrosion can also be caused by a reaction between the battery’s terminal posts, connectors, and lugs. As most connectors are made of copper, the resulting deposit will typically be blue in color, indicating the presence of copper sulfate.

How to Clean Deposits and Remove Corrosion on Your Batteries

Before cleaning your batteries, always take proper safety precautions like gloves and eye protection. In addition, make sure to disconnect the battery before cleaning it.

There are several ways to clean potassium carbonate, lead crystals, and sulfate build-up on your batteries. The best cleaning method depends on the type of battery and the severity of the build-up.

Some common methods include:

  • Wiping the terminals with a damp cloth or a solution of baking soda and water. This can help remove minor corrosion and prevent further build-up.
  • Using a specialized battery cleaning solution or corrosion neutralizer to dissolve and remove the build-up.
  • Scraping away the build-up using a non-metallic brush or tool, such as a toothbrush or plastic scraper.
  • Applying a protective coating, such as petroleum jelly or dielectric grease, to the terminals to prevent further corrosion.
  • Using a Q-tip cotton swab dipped in vinegar. The vinegar’s acidity helps remove the alkaline deposits on the terminals. You can then use a swab dipped in water to rinse off the terminals.

If you are looking for a specialized battery cleaning solution, I recommend getting the Permatex Battery Cleaner (available on Amazon). With a quick three-minute application time, this formula neutralizes corrosive acid. It dissolves stubborn corrosion, leaving all types of storage batteries and attachments in emergency power supply systems clean and refreshed.

White Substance on Batteries: A Sign of Deteriorating Battery Health?

Corrosion indicates that a battery is not functioning properly, whether it is a lead-acid or alkaline battery. In the case of a lead-acid battery, corrosion suggests some electrolyte leakage, and the lead cells or terminals are deteriorating.

It is particularly concerning when white deposits accumulate on the battery’s negative terminal (cathode), as this is a result of sulfation, which is a more severe issue than corrosion.

Sulfation occurs when lead sulfate crystals form inside the battery due to undercharging. These crystals impede the flow of ions between cells, leading to premature battery failure.

Similarly, in alkaline batteries, the formation of a white, crusty substance is a sign of leakage and oxidation of the reactive elements due to exposure to oxygen. In any case, significant corrosion on a battery is a clear indication that its useful life has come to an end.

The Bottom Line

Whether lead-acid or alkaline, batteries should always be monitored for signs of corrosion as it indicates that there may be a leakage or other issue with the reactants within the battery. Minor corrosive deposits should be cleaned immediately and checked for recurrence.

If significant corrosion is present, the battery is likely nearing the end of its useful life, and replacement is necessary.

It is important to exercise caution when handling corrosion, as the white, crusty substances formed can be harmful to health. Protective gloves should be worn whenever possible. 

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