Alkaline AA batteries are a common power source for countless household devices, but they often develop a white, crystalline substance known as corrosion. This leakage indicates that the battery’s internal chemistry has breached its casing, often damaging the electronic device. Understanding the chemical changes and mechanical failures that cause this corrosion is the first step toward effective remediation and prevention.
The Chemical Identity of Alkaline Corrosion
The white, crusty substance seen on corroded alkaline batteries is primarily potassium carbonate. Alkaline batteries use an electrolyte solution of potassium hydroxide, which is a strong, caustic base capable of damaging skin and eyes. When this electrolyte leaks out, it reacts with carbon dioxide in the air. This reaction neutralizes the liquid potassium hydroxide into the solid, white salt known as potassium carbonate. While less dangerous than the initial liquid, potassium carbonate is electrically non-conductive and corrosive to the metal contacts of the battery compartment.
Primary Triggers for Battery Leakage
Corrosion begins with a leak, which is most often caused by a buildup of internal pressure within the sealed battery cell. The most frequent cause is deep discharge, which occurs when a battery is completely drained of power, such as when it is left in a device that still draws a small current. In a deeply discharged alkaline cell, the polarity can reverse, causing a side reaction that generates hydrogen gas. This gas increases the internal pressure until it forces the potassium hydroxide electrolyte out through the battery’s seals or vents.
Mixing different types of batteries, or combining old and new batteries, also increases the likelihood of a leak. The weaker cell in the series will be forced into a deep discharge state by the stronger batteries, leading to the same internal pressure issues. Even unused batteries can leak over time as they slowly self-discharge, a process that can also generate gas.
Extreme temperatures, particularly high heat, accelerate the chemical reactions inside the battery and cause the potassium hydroxide to expand. This expansion rapidly raises internal pressure, which can compromise the seals and lead to leakage. Simple age and the natural degradation of the battery’s casing seals over many years also contribute to the risk of a leak.
Remediation and Prevention
Safe cleanup of alkaline corrosion requires protective measures, including wearing gloves and eye protection, as the residue can still be irritating. Because the residue is alkaline, it must be neutralized with a mild acid before removal. White vinegar or lemon juice are effective for this purpose.
Applying a small amount of vinegar to the corrosion with a cotton swab will cause a fizzing reaction, indicating the neutralization of the alkaline salts. Once the reaction stops, the residue can be gently scrubbed away with a toothbrush or cotton swab, then dried thoroughly. For persistent deposits, a small, non-metallic abrasive tool can be used to clean the metal contacts and ensure proper electrical flow.
To prevent future corrosion, the most effective action is to remove batteries from devices that will not be used for more than a few weeks. Storing batteries in a cool, dry place, ideally between 59 and 77 degrees Fahrenheit, helps to slow down the chemical processes that cause internal pressure buildup. Avoiding the mixing of different battery brands, ages, or types in the same device will also prevent the over-discharge of individual cells.