Magnesium alloy fluoride-free hydrazine chemical nickel plating solution and nickel plating process thereof

Abstract

The invention discloses a magnesium alloy fluoride-free hydrazine chemical nickel plating solution and a nickel plating process thereof. The nickel plating solution comprises an alkaline fluoride-free hydrazine chemical nickel plating solution and an acidic fluoride-free hydrazine chemical nickel plating solution; the pH value of the alkaline fluoride-free hydrazine chemical nickel plating solution is greater than or equal to 13, and the alkaline fluoride-free hydrazine chemical nickel plating solution consists of nickel chloride, hydrazine, a complexing agent, sodium hydroxide or potassium hydroxide, boric acid or thiourea; the pH value of the acid fluoride-free hydrazine chemical nickel plating solution is 4-6, and the acidic fluoride-free hydrazine chemical nickel plating solution consists of a nickel salt, sodium hypophosphite, citric acid and thiourea. The nickel plating process comprises the following steps: polishing, removing oil and grease, carrying out alkaline washing, pickling, activating, carrying out alkaline fluoride-free hydrazine chemical nickel plating, carrying out acidic fluoride-free hydrazine chemical nickel plating, and passivating. The plating solution is free of fluorine in component, safe in composition, and does not pollute the environment; the service life of the alkaline fluoride-free hydrazine chemical nickel plating solution is long; an outer layer of a composite coating obtained by nickel plating is an amorphous-state nickel phosphorus alloy; and the compact coating is high in compactness, relatively good in corrosion resistance and high in binding force, and has a good industrial application prospect.

Description

technical field [0001] The invention relates to an electroless nickel plating solution and a nickel plating process thereof, in particular to a fluorine-free, environmentally friendly and long-life hydrazine electroless nickel plating solution and a nickel plating process for magnesium alloys. Background technique [0002] Magnesium alloy is known as the green metal structural material in the 21st century. It has many unique advantages, such as low density, high specific strength and specific stiffness, and excellent damping, machinability, and casting performance. It has been widely used in industry. Although magnesium is rich in raw materials and ranks eighth among natural resources, its poor corrosion resistance as a structural material restricts its wider use. [0003] In the electroless nickel plating of magnesium alloys, it is necessary to avoid the strong corrosion reaction and displacement reaction between the magnesium substrate and the components of the plating so...

AI Technical Summary

Problems solved by technology

Fluoride is used in the three commonly used plating solutions, and the existence of fluoride ions not only restricts the material of the plating tank, but also is harmful to the human body and will accelerate the degeneration of teeth. The biggest problem is that fluoride ion wastewater is very Difficult to treat, the cost of wastewater treatment is very high, and it cannot be discharged into the environment in large quantities, otherwise it will cause serious environmental pollution

No buffering agent is added in the alkaline plating solution formula disclosed by CN100476024C, so that the electroless plating speed, the appearance of the coating and the combination of the coating are all unsatisfactory

[0007] At present, some people have used alkaline plating solution for magnesium alloys, and have adopted the mode of secondary nickel plating, such as the disclosed technical scheme of CN103215574A, which adopts the secondary nickel plating mode of alkaline and neutral nickel plating, but in the plating solution formula Expensive nickel acetate is used, sodium fluoride or potassium fluoride are added in the alkaline plating solution, ammonium bifluoride is added in the neutral plating solution, and fluoride is all introduced in the plating solution; the disclosed technical scheme of CN100570000C adopts Alkaline and acidic nickel plating are secondary nickel plating methods, but ammonium bifluoride is added to the alkaline and acidic plating solutions, and fluoride is still used in the plating solution, which cannot achieve fluorine-free environmental protection nickel plating, and corrosion resistance and compactness poor performance

The disclosed technical scheme of CN104694913A adopts alkaline and acidic nickel-plating secondary nickel-plating mode to realize a fluorine-free and environmentally friendly chemical nickel-plating solution, but the reducing agent used in the alkaline fluorine-free plating solution is sodium hypophosphite, and the reduction of nickel At the same time, a large amount of phosphite ions will be produced. If the reaction continues, adding hypophosphite will inevitably increase the concentration of phosphite ions. When the concentration of phosphite ions reaches 30g / L, the electroless plating will decrease rapidly. The deposition rate of nickel, phosphite ions will also form nickel phosphite precipitates with low solubility with nickel ions in the solution, making the plating solution turbid, and even catalyzing the instant decomposition of the plating solution

[0008] In addition, most of the reducing agents used in other alkaline electroless nickel plating solutions that have been reported are mainly sodium hypophosphite, aminoborane, and borohydride, and there are oxidation products of reducing agents that accumulate in the solution and cause the performance of the plating solution to gradually deteriorate. until the problem of unusable

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