GI Washer, machine component that is used in conjunction with a screw fastener such as a bolt and nut and that usually serves either to keep the screw from loosening or to distribute the load from the nut or bolt head over a larger area.
Zinc-plated washers are flat, circular steel plates with a zinc coating that prevents the steel from corroding. Zinc plating is often used to protect iron and steel from water and other elements in the air that cause corrosion. Zinc is more reactive than iron, so it oxidizes in preference to the iron object. However, the zinc coating will eventually break down and oxidize into rust. Zinc coating is most useful in environments where the metal is only occasionally in conditions where it can corrode.
