Electrolytic nickel coatings for reactive substrates

Nickel electrodeposits were produced in ethylene glycol using 0.6M concentration of respective hydrate and anhydrous nickel salts on copper substrates. These coatings were deposited at different current density values, and the purpose was to optimize electro-deposition parameters for adherent coatings on reactive substrates. The resultant coatings in both hydrate and anhydrous electrolytic baths were then characterized by XRD and SEM. XRD results revealed that high purity nickel deposited with grain size ranging from 33 nm to 15 nm in hydrate salt and 21 nm to 18 nm in anhydrous salt bath. Texture coefficient (TC) calculated varies as a function of grain size both in hydrate and anhydrous electrolyte bath. SEM examination also confirmed nanocrystalline needle like microstructure formed at all current density values. Cyclic voltammetry and chronopotentiometry were performed to understand the deposition and dissolution mechanisms in both hydrate and anhydrous electrolytes. More than 100% current efficiency was recorded in anhydrous bath due to Ni+1 ion presences along with Ni+2 ions in both cyclic voltammetry and chronopotentiometry. Same electroplating parameters were applied to produce nickel electrodeposit on reactive substrate in ethylene glycol. Due to absence of water molecules and high current efficiency up to 80% in anhydrous bath; a good quality adherent deposit was obtained on reactive substrate as well. (author)