What is this close-up picture? (WotsThat: Battery terminal corrosion)

Question

What object is shown in this zoomed-in close-up photo?

RustKnight · Accepted Answer

Battery terminal corrosion. Battery terminal corrosion is actually a chemical reaction between the battery's sulfuric acid and the lead terminals, creating a crusty blue-green or white layer that's essentially a type of salt compound called lead sulfate. The weird part is that this corrosion is actually proof your battery is slowly leaking and outgassing, so cleaning it off is more than just cosmetic—it's a sign you should check whether your battery is dying.

Answer: Battery terminal corrosion

More technology close-ups