Method for chemical plating of nickel-boron alloy on magnesium alloy surface

Abstract

The method relates the electron alloy surface chemical plating nickel-boron alloy. The invention provides the chemical plating Ni-B alloying layer technology form AZ31B electron alloys surface, which has low cost, simple operation and good environment. The method comprises the following steps: cleaning the electron alloy with alkali and supersonic wave and acid, and activating and poaching at 60-75Deg.C; putting it into chemical plating solution at 80-90Deg.C for 2-3 hours, taking it out, and poaching, getting Ni-B alloying layer; drying at 150-180Deg.C for 30-45 min. The technology has the advantages of low cost, simple operation, no chromic compounds, good aggradation effect, high hardness, good binding force and corrosion resisting property, and wide steering range.

Description

technical field [0001] The invention relates to a process for chemically plating Ni-B alloy on the surface of an AZ31B magnesium alloy. Background technique [0002] Magnesium alloy has the characteristics of light weight, high shock absorption and heat dissipation, good casting and cutting performance, high electromagnetic immunity barrier, anti-fatigue, non-toxic, non-magnetic, low crack tendency and recyclable use, etc., and has been successfully used in Transportation, computer, communication, consumer electronics, national defense and military industry and many other fields. However, the corrosion resistance of magnesium is poor, which is the bottleneck restricting the potential of magnesium alloys. On the other hand, due to the low hardness and poor wear resistance of magnesium alloys, the large-scale use of magnesium alloys is restricted. In order to improve the corrosion resistance and wear resistance of magnesium alloys, appropriate surface modification is necessa...

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Problems solved by technology

[0005] 2) The binding force of direct electroless plating Ni-P with fluoride activation is not high (Chinese patent: 02144834.5), and pre-plating is required in order to improve the binding force, resulting in cumbersome process (Corrosion Science, 2004, 46: 1467-1477)

[0010] 2) The Mg alloy is active, and loose MgO will form rapidly on the surface of the alloy, which hinders the formation of metal bonds between the deposited metal and the substrate

[0011] 3) Traditional electroless nickel plating generally chooses nickel chloride or nickel sulfate as the main salt, and most plating solutions are corrosive to magnesium, especially those containing Cl - , SO 4 2- In the salt solution of Mg, the corrosion rate of Mg is larger; under no stress state, the corrosion rate of Mg-Al-Zn alloy in different anion media is Cl - > SO 4 2- >NO 3 - >Ac - >CO 3 2-

But the price of basic nickel carbonate is too high, and the cost of chemical plating doubles; in addition, basic nickel carbonate is insoluble in water, and must be dissolved with hydrofluoric acid before preparation, and the dissolution process is time-consuming and low in production efficiency; Another problem with nickel carbonate as nickel salt is that the bath life is short, because when nickel is supplemented during long-term use of the bath, the concentration of fluoride ions in the bath will inevitably increase, and the solubility of nickel fluoride is very small, and eventually the electroless plating process Precipitation is formed in the medium, causing nickel to be unable to be replenished and shortening the service life of the plating solution

[0012] 4) Sodium borohydride as a reducing agent in electroless Ni-B alloy plating is prone to hydrolysis in acidic and neutral solutions. In order to avoid hydrolysis and obtain a higher deposition rate, the plating solution must be kept strongly alkaline, and at pH In the alkaline medium >11, insoluble Mg(OH) will form on the surface of Mg 2 film, which affects the bonding of the coating to the substrate

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