How should you treat a lead-acid battery compartment to protect it from corrosion?

• A. Acrylic primer only
• B. Paint with asphaltic tar-base paint or polyurethane enamel
• C. Leave bare metal
• D. Seal with silicone caulk

Answer: (B)

Corrosion protection of a lead-acid battery compartment relies on creating a durable, chemical-resistant barrier between the metal and any acidic electrolyte or fumes. Lead-acid batteries can vent sulfuric acid and moisture, which quickly corrodes bare metal. A coating that adheres well to metal and withstands acidic conditions is essential.

Painting the interior and exterior surfaces with an asphaltic tar-base paint or a polyurethane enamel provides that tough, protective film. These coatings resist chemical attack from battery acid and dampness, seal small leaks, and prevent moisture from reaching the metal. They also tolerate temperature changes common in aircraft environments, helping to maintain the enclosure’s integrity over time.

Acrylic primer alone isn’t enough because primers are meant to prepare surfaces for paint, not provide long-term chemical resistance in a corrosive environment. Leaving the metal bare invites rapid corrosion. Silicone caulk is useful for sealing joints, but it isn’t a durable, all-around protective coating for an entire battery compartment interior, and it can degrade under acid exposure.