Also known as alloy k500, Monel K500 fasteners and flanges are comprised of a nickel alloy that combines the outstanding corrosion resistance of Monel 400 with increased strength and hardness. Stronger than 400, alloy K500 even retains this strength in corrosive conditions, resisting both pure and salt water, as well as non-oxidizing mineral acids, salts, alkalis, and sour gas.