Corrosion behaviour of electrodeposited Ni–Sn–P alloys

Abstract

Ni–Sn–P alloys with a stannous content of 2·91–4·05 wt-% and a phosphorous content of 13·54–14·56 wt-% produced as a coating on copper by constant current electrodeposition were studied, with regard to their corrosion behaviour upon immersion in 10 wt-% H₂SO₄ solutions. The corrosion resistance of Ni–Sn–P alloy improved with increasing stannous content. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy confirmed the formation of Sn and P enriched layers at the alloy surface. After corrosion, a layer of passive film composed of SnO₂, Ni(OH)₂ and Ni₃(PO₄)₂ was formed on the surface, which could prevent the contact between metal surface and corrosive liquid.