The influence of an aqueous-butanol plating bath on the microstructure and corrosion resistance of electrodeposited nickel coatings

The effects of higher concentrations (5 and 10%) of an organic modifier, butanol, added to an aqueous electroplating solution for nickel deposition have been studied. Nickel coatings were deposited on steel substrates from a modified all-sulfate bath with 5 and 10% additions of butanol under acidic conditions, while a modified pulse potential was applied. X-ray diffraction of the resulting nickel coatings showed a preferred (220) orientation for the crystal structure. The coatings were nanocrystalline with particle sizes between 16 and 35 nm as calculated from Williamson–Hall analysis. No cracking of the films was observed in the scanning electron microscopy images, even as the percentage of butanol increased, as typically is observed in other aqueous-organic baths. Corrosion resistance of the nickel coatings in a 3.5% sodium chloride solution was best for coatings deposited from plating solutions containing 5 and 10% butanol. E corr was shifted from −0.405 V for the nickel coating from the additive-free bath to −0.234 V for the nickel coating from the 5% butanol solution. EIS results indicated a twofold improvement in charge transfer resistance for nickel coatings deposited when butanol was used in the plating bath. The advantages of using higher percentages of organic modifiers like butanol to enable the use of non-electroactive particles for production of composite coatings are discussed.