The resistance of copper to atmospheric and water corrosion is good, hence their usage for producing rust free nails. The metal develops adherent protective coatings, initially of oxide, but subsequently thickening to give a familiar green patina on roofs. Because copper is largely unaffected by sea water,copper nails are used as fastenings in wooden boats.We produce round shank copper nails as well as square shank nails.These square shank nails can be used as a rivet or for face nailing.Square shank provides greater holding "gripping" power than conventional round shank nails.