In recent years, daily necessities have been constantly updated, and higher requirements have been placed on surface decoration. Multi-color electroplated finishing parts are very popular among consumers, and they are widely used, ranging from signs and crafts to hardware, locks, lamps, glasses, watches and clocks, etc. There are applications. Plastics are difficult to plate materials. Although there are mature processes and reports, there are still reports on two-color plating and multi-color plating processes. At present, the processing price of electroplating (imitation gold + chromium) of a certain plastic trademark sign is as high as 8-9 yuan/dm2, and the market is wide and the benefits are good. This article provides an introduction to the production of a more mature two-color plating process.
1. Process and precautions
In addition to stress → chemical degreasing → chemical roughening → hydrochloric acid washing → direct activation of colloidal palladium → degumming → electroless nickel plating → brush scrubbing • flash plating (pyrophosphate plating) → acid bright copper plating → bright nickel plating → thin Acid activation→plating imitation gold→passivation→drying→local varnish→drying→removal of local imitation gold layer→dilute H2SO4 activation→chrome plating→drying→testing. The above process omits the water washing process. But water washing must be there, and it must be thoroughly cleaned. Water washing after activation and degumming is strictly prohibited. Prevent scratches and scratches between parts during each operation. When the parts are loaded, basketed or poured out from the net or basket, it should be lightly operated. It is best to pour it into the basin of water and use the buoyancy of water to prevent scratches between the parts.
1.1 In addition to stress, the plastic parts were placed in an oven and kept at 70 ° C for 2 h.
1.2 chemical degreasing
Sodium hydroxide 40g / L, sodium phosphate 30g / L, sodium carbonate 20g / L, OP emulsifier 1 ~ 3g / L, θ60 ~ 70 ° C, t10 ~ 15min
During the degreasing process, the plastic parts should be gently agitated to speed up the degreasing. The crude recovered liquid may also be warmed to a temperature of not more than 70 ° C to remove oil.
1.3 Chemical roughening [1] CrO3400g / L, H2SO4 (d = 1.84) 200mL / L, H2O600mL / L relative density of 1.45θ70 ° C, t10 ~ 15min as long as strictly in accordance with this formula and working conditions, no coarsening or Over-grown.
1.4 Hydrochloric acid washing HCl (d=1.19) 100～200mL/L, t1～3min hydrochloric acid washing can remove the residual crude liquid and adsorbed Cr3+ on the plastic surface. After washing with hydrochloric acid, it was observed with the naked eye that the plastic surface became white with a light dark green color.
1.5 colloidal palladium direct activation method PdCl2 · 2H2O 0.5 ~ 1g / L, SnCl2 · 2H2O50 ~ 100g / L, HCl (d = 1.19) 200 ~ 300mL / L, θ50 ~ 60 ° C, t5 ~ 10min palladium chloride concentration not too High, otherwise the cost of the distribution tank is high, and the loss is large. In some of the data reported in [2], the palladium chloride concentration is less than 0.5g/L, which proved to be unfeasible in production. Even if the activation time is extended to 30min or more, the temperature will increase to above 60°C. Exhibited plastic, low production efficiency and low yield. In order to prevent the washing water from being brought into the dilution of the activation liquid to cause precipitation, the plastic part is pre-soaked in the recovered liquid after the colloidal palladium solution for 5 minutes before entering the colloidal palladium direct activation liquid, and the colloidal palladium activation is directly performed without washing. It is forbidden to add the non-returned nickel layer of the electroless nickel plating to the colloidal palladium solution for reactivation, so as to prevent the colloidal palladium activation solution from introducing Ni2+ and reducing the activity and stability of the activation solution.
1.6 Dissolving NaOH 100～300g/Lt3～5min Alkaline solution dissolving method is faster than acid solution dissolving, completely without heating, and acid degumming requires more concentrated acid and heating.
1.7 Electroless nickel plating, pyrophosphate copper plating, acid bright copper plating, bright nickel plating, gold plating and chrome plating solution composition, preparation, maintenance and use are the same as conventional plating liquid, please refer to relevant information.
1.8 Brushing The surface of the electroless nickel plating layer may have solid particles or other contaminants. It is easy to produce rough and matte after plating. This is obvious on large-area plating parts, so a brush cleaning process is added. Do not use a too hard brush when brushing to avoid scratching the electroless nickel layer.
After 1.9 varnish is imprinted with gold, passivated and then transparent varnish can improve the anti-tarnishing ability of the gold layer, and also play an insulating role to prevent the gold layer from being plated with chromium. Plastic parts are not resistant to temperature, and transparent varnishes are required to be self-drying or low-temperature drying at room temperature. Care should be taken when applying local varnish to prevent lacquering on the chrome-plated parts. If you need to dry the paint film, the temperature should not exceed 70 °C.
2 Conclusion
The multi-color electroplating market has good prospects and good returns, but there is no report for reference at the beginning. The two-color electroplating product described in this article, the golden yellow (imitation gold) background brings out a white (chrome) pattern, and the appearance is very beautiful. However, the bright nickel layer is subjected to many processes such as gold plating, passivation, drying, varnishing, drying, partial removal of the imitation gold layer, etc., and it takes more than 24 hours, and severe passivation occurs. Despite the long-time immersion activation of dilute H2SO4, the chrome-plated quality rate is still too low (up to 40%), which restricts economic benefits. I believe that with the efforts of electroplating workers, other such as satin nickel + imitation gold, black nickel + imitation gold, red bronze + black nickel, white nickel + black nickel + gold, red bronze + black nickel + imitation gold... Multi-color plating processes are bound to become more mature.
1. Process and precautions
In addition to stress → chemical degreasing → chemical roughening → hydrochloric acid washing → direct activation of colloidal palladium → degumming → electroless nickel plating → brush scrubbing • flash plating (pyrophosphate plating) → acid bright copper plating → bright nickel plating → thin Acid activation→plating imitation gold→passivation→drying→local varnish→drying→removal of local imitation gold layer→dilute H2SO4 activation→chrome plating→drying→testing. The above process omits the water washing process. But water washing must be there, and it must be thoroughly cleaned. Water washing after activation and degumming is strictly prohibited. Prevent scratches and scratches between parts during each operation. When the parts are loaded, basketed or poured out from the net or basket, it should be lightly operated. It is best to pour it into the basin of water and use the buoyancy of water to prevent scratches between the parts.
1.1 In addition to stress, the plastic parts were placed in an oven and kept at 70 ° C for 2 h.
1.2 chemical degreasing
Sodium hydroxide 40g / L, sodium phosphate 30g / L, sodium carbonate 20g / L, OP emulsifier 1 ~ 3g / L, θ60 ~ 70 ° C, t10 ~ 15min
During the degreasing process, the plastic parts should be gently agitated to speed up the degreasing. The crude recovered liquid may also be warmed to a temperature of not more than 70 ° C to remove oil.
1.3 Chemical roughening [1] CrO3400g / L, H2SO4 (d = 1.84) 200mL / L, H2O600mL / L relative density of 1.45θ70 ° C, t10 ~ 15min as long as strictly in accordance with this formula and working conditions, no coarsening or Over-grown.
1.4 Hydrochloric acid washing HCl (d=1.19) 100～200mL/L, t1～3min hydrochloric acid washing can remove the residual crude liquid and adsorbed Cr3+ on the plastic surface. After washing with hydrochloric acid, it was observed with the naked eye that the plastic surface became white with a light dark green color.
1.5 colloidal palladium direct activation method PdCl2 · 2H2O 0.5 ~ 1g / L, SnCl2 · 2H2O50 ~ 100g / L, HCl (d = 1.19) 200 ~ 300mL / L, θ50 ~ 60 ° C, t5 ~ 10min palladium chloride concentration not too High, otherwise the cost of the distribution tank is high, and the loss is large. In some of the data reported in [2], the palladium chloride concentration is less than 0.5g/L, which proved to be unfeasible in production. Even if the activation time is extended to 30min or more, the temperature will increase to above 60°C. Exhibited plastic, low production efficiency and low yield. In order to prevent the washing water from being brought into the dilution of the activation liquid to cause precipitation, the plastic part is pre-soaked in the recovered liquid after the colloidal palladium solution for 5 minutes before entering the colloidal palladium direct activation liquid, and the colloidal palladium activation is directly performed without washing. It is forbidden to add the non-returned nickel layer of the electroless nickel plating to the colloidal palladium solution for reactivation, so as to prevent the colloidal palladium activation solution from introducing Ni2+ and reducing the activity and stability of the activation solution.
1.6 Dissolving NaOH 100～300g/Lt3～5min Alkaline solution dissolving method is faster than acid solution dissolving, completely without heating, and acid degumming requires more concentrated acid and heating.
1.7 Electroless nickel plating, pyrophosphate copper plating, acid bright copper plating, bright nickel plating, gold plating and chrome plating solution composition, preparation, maintenance and use are the same as conventional plating liquid, please refer to relevant information.
1.8 Brushing The surface of the electroless nickel plating layer may have solid particles or other contaminants. It is easy to produce rough and matte after plating. This is obvious on large-area plating parts, so a brush cleaning process is added. Do not use a too hard brush when brushing to avoid scratching the electroless nickel layer.
After 1.9 varnish is imprinted with gold, passivated and then transparent varnish can improve the anti-tarnishing ability of the gold layer, and also play an insulating role to prevent the gold layer from being plated with chromium. Plastic parts are not resistant to temperature, and transparent varnishes are required to be self-drying or low-temperature drying at room temperature. Care should be taken when applying local varnish to prevent lacquering on the chrome-plated parts. If you need to dry the paint film, the temperature should not exceed 70 °C.
2 Conclusion
The multi-color electroplating market has good prospects and good returns, but there is no report for reference at the beginning. The two-color electroplating product described in this article, the golden yellow (imitation gold) background brings out a white (chrome) pattern, and the appearance is very beautiful. However, the bright nickel layer is subjected to many processes such as gold plating, passivation, drying, varnishing, drying, partial removal of the imitation gold layer, etc., and it takes more than 24 hours, and severe passivation occurs. Despite the long-time immersion activation of dilute H2SO4, the chrome-plated quality rate is still too low (up to 40%), which restricts economic benefits. I believe that with the efforts of electroplating workers, other such as satin nickel + imitation gold, black nickel + imitation gold, red bronze + black nickel, white nickel + black nickel + gold, red bronze + black nickel + imitation gold... Multi-color plating processes are bound to become more mature.
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