Nickel Ingots. Nickel, (Ni) is a soft, malleable, and ductile metal with the atomic number 28. It is soluble in acids and resists corrosion in air. Nickel is used as an industrial catalyst and to add corrosion resistance and strength to steel. It is also used in alloys such as Invar and Mumetal. Nickel is found in the minerals pentlandite (nickel sulphide), pyrrhoite and garnierite.