Electrodeposition of Nickel-Phosphorus Alloy from Sulfamate Baths with Improved Current Efficiency

Abstract

In this study, nickel-phosphorus (Ni–P) deposits were electroplated from the nickel sulfamate bath containing phosphorous acid using a pulse current, with emphasis on the effect of current density, duty cycle, and frequency of the pulse current. Experimental results show that both the deposit phosphorus content and current efficiency were substantially enhanced by employing the pulse current, preferentially at low duty cycles. The underlying difference for the dc and pulse currents on the effect of deposit phosphorus content and current efficiency can be explained by the detailed half-reactions relevant to incorporation of phosphorus into Ni–P alloys. Less variation in surface proton, and concentration due to the diffusion recovery during the time off of a pulse current is believed to play an important role in the improvement of the plating process.