Composition, structure and corrosion characteristics of Ni–Fe–P and Ni–Fe–P–B alloy deposits prepared by electroless plating

The composition, structures and corrosion resistance of electroless Ni–Fe–P and Ni–Fe–P–B alloy deposits were studied. The deposits were prepared by controlling the concentration of NaH2PO2 and KBH4, the metallic salt ratio FeSO4/(FeSO4+NiSO4) or pH value, which varies from 18 to 48 g/l NaH2PO2, from 0.1 to 1.0 FeSO4/(FeSO4+NiSO4), from pH 8 to 13 for Ni–Fe–P deposits, from 13 to 48 g/l NaH2PO2, from 0 to 1.4 g/l KBH4, from 0.1 to 1.0 FeSO4/(FeSO4+NiSO4) and from pH 9.5 to 12.5 for Ni–Fe–P–B deposits. Both amorphous and crystalline structures were obtained by changing these parameters. The maximum iron content of approximately 38 at.% was obtained at 28 g/l NaH2PO2 or a metallic salt ratio of 0.5 for Ni–Fe–P, 0.4 g/l KBH4 for Ni–Fe–P–B alloy deposits. The deposits with medium NaH2PO2 content showed less weight loss after immersion in acidic and alkaline solution during corrosion tests, which ranged in formation range of the amorphous structure for Ni–Fe–P–B deposits. A trace of KBH4 added can decrease corrosion resistance in alkaline solution and was not obvious in the composition of Ni–Fe–P deposits.