Formula And Operation Skills Of Plastic Electroplating-gold-like Electroplating

Formula and operation skills of plastic electroplating-gold-like electroplating.
Huizhou Boluo Tenglong Technology Co., Ltd. serves you wholeheartedly! Mainly engaged in plastic hydroelectroplating processing, with plastic injection molding processing, mold processing and so on!
The production of plastic hardware has developed rapidly since the reform and opening up. In addition to the use of pure gold coating for specific high-grade products, 24K imitation gold plating is more common. In the decorative electroplating process, imitation gold plating is the most widely used electroplating process. Lighting, locks, ceiling fans, bags, lighters, glasses frames, tie clips and other products have a variety of appearance, but most of them are still gold coating, and there are many ways to obtain the gold appearance, such as real gold plating, copper zinc plating, copper tin or copper tin imitation gold, gold electrophoretic paint, gold glue technology and so on. Among them, imitation gold plating is a widely used process.
I. Formula of imitation gold plating bath.
1. Cyanide plating solution is the most commonly used and stable in copper-zinc, copper-tin or copper-zinc-tin imitating gold plating solution. Domestic factories generally use their own alloy plating solution. We are happy to share the team's many years of on-site experience with you as follows:
Cuprous 28-30 grams.
60-65 grams of sodium cyanide.
7-8 grams of zinc cyanide.
Potassium sodium tartrate 6-8 grams.
10-12 grams of potassium hydroxide.
1.5-2.5 grams of sodium Stannate.
Trace cobalt sulfate.
two.. Foreign factories and some domestic factories also use bronze salts provided by foreign electroplating raw materials manufacturers to imitate gold. The process formula and operating conditions are as follows:
Bronze salt 80~100g/L.
Ammonia 1~2ml/L.
The temperature is 35-50 degrees.
Bath composition:
Cu 15~18g/L.
Zn 6~8g/L.
Free NaCN 8~10g/L.
Second, imitation gold plating is not only the optimization of the ternary content and temperature of complex and copper, zinc and tin in the formula, but also the choice of current and time. The current is divided into three stages with different amperes, and the third current is controlled by time. Pull on the high, medium and low cathode current, first high and then low, the hanger shakes gently, and under the action of current, the coating is made of blue and white "light yellow" and imitates gold color of nearly 24K.
Third, the function and control skills of each component.
1. Sodium cyanide.
With the increase of its content, on the one hand, it is beneficial to the formation of Zn (CN) J-1 and reduce the amount of zinc precipitated in the plating bath; on the other hand, it enhances the complexation degree of copper cyanide ion with cyanide and reduces the precipitation amount of copper. From the experience of our team's long-term control: the right amount of sodium cyanide can turn the reddish color to yellow, or it may turn too much to white. We must keep in mind the process of color change according to the change of sodium cyanide.
In the new adjustable solution, the complex transformation between various ions can not be completed immediately. In order to make the various complex ions reach a steady chemical equilibrium, it is necessary to evenly stir the complex for a period of time after adding sodium cyanide or sodium hydroxide.
two.. Sodium hydroxide.
1) it is the second complexing agent of zinc and the only complexing agent of tin. The ratio of zinc to tin in the alloy coating directly affects the color. With the increase of the content, the ratio of zinc precipitation also increases. If the coating is reddish, the addition of sodium hydroxide may change the color to yellow, but the prerequisite is that there is enough zinc and not too high sodium cyanide in the solution. On the contrary, the content of sodium hydroxide is too low, which is not conducive to the precipitation of zinc. In order to obtain the ideal imitation gold color, it is necessary to increase the super-ratio zinc content to make up for the deficiency of zinc precipitation.
2) in addition, our team would like to inform you that sodium hydroxide is too low, which is not conducive to the stability of sodium Stannate, and even gradually hydrolyzes into meta-tin acid impurities and precipitates at the bottom of the tank. This reaction is irreversible in the tank. Once the complex is not good, no matter how to increase the sodium hydroxide after that, meta-stannic acid will no longer dissolve and return to sodium Stannate.
3) there is another situation: when the ratio of copper to zinc in the solution is appropriate, sometimes too high sodium hydroxide will make the imitation gold show a reddish khaki (like yellow mud soil) or zinc red. If this zinc red is regarded as copper red with too much copper in the coating, it will be a mistake to continue to supplement the amount of sodium hydroxide or zinc. At this time, acidic substances should be used to reduce the amount of sodium hydroxide and turn zinc red into gold.
3. Rochelle salt.
It is the third complexing agent and has a weak complexing effect on both copper and zinc. The addition of potassium sodium tartrate can improve the brightness of the gold-like coating, especially in the process of electroplating for a long time, it can maintain a good brightness, play the role of semi-brightener and activate the anode.
4. The amount of cobalt sulfate is very small, about 0.05~0.10g/L, which can promote the imitation of gold and soften the light of gold.
IV. Technological conditions.
In addition to the effects of these main salts, the process conditions are also very important for imitation gold plating, such as:
The main results are as follows: (1) temperature is used as an auxiliary means of color blending, and the increase of temperature is beneficial to the electrolytic precipitation of copper and increase the red hue of imitation gold color. It is generally appropriate to adopt 40-50 ℃, which can reach 60 ℃ if necessary, which can be adjusted according to the needs of color and the composition of the solution. The increase of temperature can improve the conductivity of the solution and make the color uniform and bright. However, too high temperature will accelerate the decomposition and consumption of sodium cyanide, which is not conducive to the stability of the solution.
(2) current density. In order to obtain perfect imitation gold, it is required that the ratio of each metal and its ratio to the complexing agent should be satisfied that the amount of precipitation of each metal at a certain potential and current reaches the best proportion of imitation gold, in order to achieve repetitive accuracy of current control, in order to ensure the reproducibility of color, a special three-gear current timing controller should be used. The current controller consists of three adjustable time relays, which automatically turn on and off three voltage regulators according to the given time, and input the three step-down fixed voltages into a transformer in turn each time. After the output current is rectified, the three different sizes of the current are input into the gold-like slot according to the given voltage. The power supply device of this kind of imitating gold slot is different from that of other grooves, and the three-step current is divided into impulse current, transition current and imitation gold current. It is very important to control and select the time and size of each current, and the last gear is the most important.
(3) imitating gold time. The total time of each stage is 20: 30s, the length of impulse current is not caused by local scorch or the decrease of brightness, and the time of imitating gold current is to obtain a uniform imitation gold with sufficient chromaticity. The time of the third gear current should be allocated reasonably.