Multilayer nickel plating process for aerospace aluminum alloy parts
[Introduction]The cadmium plating process of aerospace aluminum alloy parts urgently needs to find environmentally friendly alternative technologies.[Method]A multilayer nickel plating process was developed,including the following steps:chemical degreasing,ultrasound degreasing,alkaline etching,bright dipping,desmutting,slight etching,first zinc immersion,zinc stripping,secondary zinc immersion,electroless nickel pre-plating,semi-bright nickel plating,high-sulfur nickel plating,bright nickel plating,electrolytic passivation with rare earth,and drying.[Result]The coating obtained by the process endured 168 hours of neutral salt spray test without any corrosion product on its surface,did not blister or peel off during thermal shock test at 220 ℃,and remained unchanged in appearance after 1 000 hours of steady-state damp heat test at temperature 40 ℃ and relative humidity 93%.[Conclusion]This process overcomes the disadvantage that a single electrolessly plated nickel coating has no electrochemical protection effect on the aluminum alloy substrate,and replaces the traditional chromate electrolytic passivation method with a newly developed rare earth electrolytic passivation method,having environmental friendliness and good application prospect.
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