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

Abstract

In this study, nickel-phosphorus ͑Ni-P͒ 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 NiP alloys. Less variation in surface proton, Ni 2+ and H 3 PO 3 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.

Study of the Corrosion Behavior of Nanocrystalline Ni-P Electrodeposited Coating

“…Both the strength of the electric field around the pits and the electrolyte passage created by the pit hole can provide the continuous corrosion near the area. In addition, the layered microstructure of the coating, which is likely to result from the slight variation in the P content during electrodeposition, [13] gives way to the transverse propagation of the corrosion. Thus, the weight loss due to the corrosion increases drastically (Table I).…”

“…Accordingly, the cathodic efficiency of the deposition was approximately 75 tõ 80 pct, which was consistent with that of a previous study. [13] With the (111) XRD peak and the Scherrer equation, we calculated the grain size to be approximately 4.3 nm, which demonstrated the existence of a nanocrystalline structure. Finally, the hardness of the coating was 570 to~590 Hv and the deposited stress was -22.1 MPa.…”

“…Those deposition parameters were adopted from the previous work of Lin and his co-workers. [13] B. Corrosion Test…”

Examining the effect of electrosynthesis conditions on the Ni-P alloy composition

“…The Ni-P alloy composition, in turn, depends on the type of the employed electrolyte. As a rule, electrosynthesis of the Ni-P alloy is performed from the sulfate [11,12] or sulphamate [2,13] electrolytes. At the same time, it was proposed to apply in the modern technologies of the alloy electrosynthesis a new electrolyte based on methanesulfonic acid [14,15].…”

Pulse-electrodeposited NiP–SiC composite coatings

“…A strong pH dependency is determining this deposition mechanism, since hydrogen has a significant role for the reduction of the P to form the nickel-phosphorous alloy. Two reaction mechanisms, direct and indirect have been proposed for the co-deposition of phosphorous into nickel matrix [9][10][11]. According to the half reaction, Ni 2+ and protons can be reduced directly at the cathode in the nickel electrolyte containing phosphorus acid (reactions (1)-(3)).…”