Effect of Sodium Vinyl Sulfonate on the Microstructure and Corrosion Resistance of Ni–Co Alloy Coatings

The present work discusses the optimization of the sulfate bath utilizing a novel sodium vinyl sulfonate (SVS) as a chemical additive for bright and uniform Ni–Co alloy deposits on mild steel (MS). The coating parameters, such as pH, rate of stirring, temperature, role of current density (CD) on hardness, thickness, surface feature, phase behavior, and elemental composition, are systematically determined using various characterizations. The results confirm the anomalous codeposition behavior with Co depositing preferentially over Ni. The increased CD resulted in progressive enhancement in coating thickness, while the hardness improves up to the optimal CD and subsequently decreases. The corrosion behavior of the deposited Ni–Co alloy coating indicates that at a CD of 4 A dm −2 , it exhibits the decreased corrosion rate, which occurs with a composition of 16.7 wt% Ni and 80.1 wt% Co. Based on the experimental findings, a bright, dense Ni–Co coating on MS specimens showed enhanced corrosion resistance and has a potential application in defense, aerospace, and automobiles.