Nickel (Ni) is a silvery-white, lustrous metal with a slight golden tinge. It belongs to the transition metals and is hard, ductile, and ferromagnetic. In optics, nickel is commonly used as a coating material. Nickel coatings can be applied to various substrates to provide protection, reduce reflectance, or to promote adhesion for subsequent coatings. Moreover, electroplated nickel can serve as a mold surface for the precision replication of optical components. Beyond its optical applications, nickel is extensively used in many other industries, primarily in the production of stainless steel and other nickel alloys. It is also a key component in rechargeable battery systems, like those found in electric vehicles and portable electronics. Nickel's natural resistance to corrosion and its alloying properties make it a valuable metal in various engineering applications.