*5.2. Sulfate Baths*

Sulfate-based baths offer good electrodeposition prospects owing to their relative affordability compared to other baths and their ability to deposit high Co content coatings [64]. These baths contain both sulfate compounds as well as Ni chloride. The Ni chloride acts an additional source of Ni2<sup>+</sup> ions in the electrolyte and this influences the thickness of the deposited coatings. The Cl− ions from the Ni chloride increases conductivity of the electrolyte solution by causing dissolution of Ni anodes [72,73]. Internal stresses in deposited coatings have been observed to decrease where chlorides are absent in electrolytes. Absence of Cl− ions is favorable in processes where the consumable anodes remain unused. However, they are used together with other reactive agents where the anodes are consumed during the electrodeposition process [74,75].

### *5.3. Sulphamate Baths*

Sulphamate and sulphamate–sulfate baths have been reported to deposit qualified and coherent Ni–Co structures [68]. For the case of high-speed electrodeposition, nickel sulphamate baths containing boric acid have been preferred over watts baths because of the ease of obtaining relatively thicker coatings with less internal tensile stresses [76]. Ni–Co coatings deposited from sulfamate–sulfate baths have been reported to have smoother and finer surfaces and this can be attributed to lower stresses being generated in coatings deposited with these baths [68].

#### **6. Additives**

Additives are added into the electrolyte bath during electrodeposition to increase the range of current density, change physical and mechanical properties, reduce the size of crystallites by reducing growth, increase the coating's luster, reduce nanoparticle agglomeration, and reduce internal stresses generated during the deposition process [35].
