Galvanized nails are used mainly in construction, specifically roofing. They get their name from a process they undergo called galvanization. This process adds a protective zinc coating to the nail that prevents rusting and corrosion. The coat of zinc is smoothly applied through electroplating, which galvanizes the nail through an electrical current. Galvanized nails are created to last the life of a roof or other outdoor structure. They do not work well with treated wood, redwood or cedar lumber and quickly become corroded when paired with these materials.
Examine the nail visually and note the color of the nail. A galvanized nail has a silvery gray color attributable to the zinc coating.
Rub a fingertip across the shaft of the nail. Galvanized nails often have a rough finish. Occasionally, a galvanized nail looks like the coating is "running" due to it having been dipped in melted zinc.
Note the size of the nail. Galvanized nails are usually short to moderate in length and have a large nailhead, as opposed to headless finishing nails.