Black Nickel Coatings: From Plating Techniques to Applications

Black nickel coatings are pursued for both decorative purposes and advanced applications, including solar collectors, space technologies, and optical devices. The term “black nickel” typically refers not only to nickel but also to nickel alloys that can exhibit the characteristic black coloration, either bright or matte. This review provides an in-depth look at various techniques for producing black nickel coatings, focusing on both electrodeposition and electroless deposition methods. The discussion covers the different bath compositions and deposition conditions used to achieve the distinctive black color. The origins of black coloration in electrodeposited nickel and its alloys are shown in detail, emphasizing the crucial role of bath components and the formation of black compounds such as oxides, sulfides, and/or the nickel–zinc intermetallic compound. This review also highlights the necessity of oxidizing acid etching to blacken Ni–P electroless deposits, leading to the formation of a thin layer of black nickel oxides on a porous surface. The key properties of black nickel coatings are discussed, along with their relevance for various practical applications.