Anti-corrosion nanoparticle compositions include a carrier and a plurality of nonionic metal nanoparticles. The metal nanoparticles can be spherical-shaped and/or coral-shaped metal nanoparticles. The nanoparticles are selected so as to locate at the grain boundaries of a metal or metal alloy when the anti-corrosion composition is applied to the metal or alloy, thereby reducing or preventing intergranular corrosion of the metal or alloy.