镁合金化学镀Ni-W-P合金

Electroless Ni-W-P coating on magnesium alloy

将AZ91D镁合金无铬处理后,以硫酸镍和钨酸钠为主盐,柠檬酸钠和碳酸钠为复合络合剂,在碱性镀液中通过调整镀液组成,得到W含量较高的Ni-W-P合金镀层。此镀层中W及P的质量分数分别为4.50%和4.84%。通过孔隙率和极化曲线测量了此镀层的耐蚀性能,表明该镀层能够很好地提高AZ91D镁合金的耐蚀性。

Electroless Ni-W-P coating with high content of W has been developed on chromium-free pretreated AZ91 Dmagnesium alloy by using an alkaline-citrate-based baths,in which nickel sulphate and sodium tungstate were used as metal ion sources,and sodium hypophosphite was used as a reducing agent.One important modification of the Ni-W-P electroless bath is the addition of sodium carbonate,which works as complexing agent,accelerator and buffer.Codeposition of tungsten resulted in ternary Ni-W-P coating with phosphorus content of 4.84 wt.%and tungsten content of 4. 5 wt.%,respectively.Both the electrochemical analysis and the porosity test revealed that the ternary Ni-W-P coating exhibited good corrosion resistance in protecting magnesium alloy.