Process flow of magnesium and magnesium alloy direct nickel plating
Magnesium and magnesium alloys have high electrochemical activity, that is, high oxidation tendency, and most acid solutions have strong corrosive effects on them. These two points make the electroplating of magnesium alloys have a series of characteristics. It can only be directly electroplated with zinc and nickel on magnesium and magnesium alloys. At the same time, it cannot be used as the final coating and can only be used as the base for other coatings. In principle, the preparation before magnesium alloy plating is similar to that of other metals. The first is cleaning to remove contaminants. The cleaning methods include steam degreasing, emulsion cleaning and alkaline cleaning. The second is to polish according to the required surface finish, spray glass or plastic, pickle, and deburr. Before nickel or zinc plating, the surface of the workpiece must be activated.
Magnesium alloy electroless nickel plating process: traditional DOW immersion nickel method, direct electroless plating method. The former process is stable, the coating is good, and it is used much, but it contains chromium, which is harmful to the human body and harmful to the environment. It should be used as little as possible or not used. The latter process is simple, has little impact on the environment, simple wastewater treatment, and good film bonding, which has become the mainstream process of magnesium electroplating. Before nickel plating, it must be cleaned twice: firstly with chromic acid-nitric acid solution, and then with hydrofluoric acid solution.
Usually two chemical etching and washing will produce surface pitting corrosion, which provides a good mechanical anchor point for the deposition of the coating. After the nickel base coating is plated on it, the surface of the coating is not as bright and smooth as the surface obtained by the zinc immersion plating process, but Same as zinc plating, this nickel plating can accept any standard plating, such as cadmium, zinc, copper, brass, nickel, chromium, gold, silver and rhodium. Electroless plating, such as gold or silver, can also be applied to this initial nickel plating.
