When using non-cyanide alkaline zinc plating brightener, the metal impurities such as copper are the ones that pose a greater threat to the quality of the coating. In this article, we will discuss the sources, effects and removal methods of copper impurities.
Why does copper impurity occur?
In actual production, if the conductive rods and conductive copper hooks used for galvanizing are immersed in the solutions of each process, a small amount of heavy metals such as copper and lead will be carried into the acid washing tank. This will result in poor adhesion of the galvanized layer, causing the zinc layer to bubble after being plated or to bubble after being left for several days or weeks.
Why is the plating solution so sensitive to copper impurities?
Because the non-cyanide alkaline zinc plating solution does not contain strong complexing agents, compared with the cyanide zinc plating solution, the non-cyanide alkaline zinc plating solution is more delicate and is more sensitive to various metal impurities.
From the dulling color of the parts after galvanizing, it can be seen that if the cyanide-free alkaline galvanizing solution contains too many impurities (such as copper impurities and other metal impurities), then it is difficult to obtain a blue-white appearance after the blue-white zinc passivation process.
Which method should be chosen to remove copper impurities?
For the metal impurities in the non-cyanide alkaline zinc plating solution, it is not recommended to use sodium sulfide for treatment. Because if too much is added, it is likely to cause burrs in the coating, which is related to the characteristics of the plating solution. The same sodium sulfide, when placed in a cyanide zinc plating tank, is a good substance that can effectively remove copper impurities and even improve the brightness and deep plating ability; however, when placed in a non-cyanide alkaline zinc plating tank, it becomes a substance that cannot stably remove copper.
So, what are the suitable methods for removing copper impurities from alkaline zinc plating solutions? There are three methods as follows:
① Zinc powder displacement method
② Low-current electrolysis method
③ Alkaline zinc plating decontaminant
About us
Guangdong Bigely Technology Co., Ltd. ,founded in 2003, is a high-tech enterprise integrating R & D，production, sales and service, specializing in the production of electroplating chemicals. As a fast growing electroplating chemicals supplier in China, Bigely has over 20 years'experience in electroplating additives production and own production base of 5000 square meters. We can produce 15,000 tons of electroplating additives every year, which can fully meet the needs of customers.
If you need our high-quality electroplating additives, please contact us. We can provide you samples for test, and also provide a series of services.
