Bright nickel plating process and bath purification technology

performance. The use of activated carbon intermittent or continuous filtration adsorption can effectively remove organic impurities in nickel plating solution. The gas impurities in nickel plating solution usually include impurities dissolved in air and carbon dioxide. Dissolving a small amount of impurities in air can lead to the formation of a bead like lattice, causing changes in the pH value of the bath solution, resulting in pitting of the coating.  In addition, it can accelerate the decomposition of the brightener.  Therefore, it should also be controlled during the production process.

 

03 Purification Technology

In the electroplating production process, the electrolyte often accumulates impurity ions due to various reasons. If the mass concentration of impurity ions exceeds the allowable range, the coating will produce various defects, such as pinholes, pitting, bubbles, black stripes or spots. In order to improve the quality of the coating and maintain its stability, it is necessary to regularly purify the bright nickel plating solution. In fact, purification technology is to take certain process measures to purify and eliminate impurities and ions generated during the plating bath solution configuration and production process, ensuring that the plating solution is in an ideal production process state, which is conducive to process control and ensures the quality of processed products. Before exploring purification technology, it is necessary to first explore the influence of impurity ions on bright nickel plating.

The influence of impurities on the brightness of nickel plating is verified by production practice and Hull cell tests. Metal and organic impurity ions affect the electroplating of bright nickel plating through the following ways: (1) In a plating solution with high pH value, iron ions will make the coating rough. (2) Copper, zinc, cadmium, and lead ions affect the low current density region, resulting in a foggy and dark to black coating. Organic impurities may also cause misty and cloudy coatings, leading to a decrease in their mechanical properties. Misty defects may occur within a wide or narrow range of current density. (3) Aluminum and silicon often cause fogging of the coating in areas with medium to high current density, which may result in hanging dust and slight roughness. (4) The mass concentration of calcium in the solution exceeds 0.5g/L (60 ℃), and the precipitation of calcium sulfate leads to needle like roughness. (5) Hexavalent chromium leads to dark bands in the coating, bubbles in the high current density area, and peeling of the coating. Hexavalent chromium, after reacting with organic substances in solution or on the cathode, may be reduced to trivalent chromium, which may produce the same mist and roughness as iron, silicon, and aluminum. (6) If the impurity ions in the solution cause significant stress in the coating and mechanical defects lead to capillary cracks, it is called macroscopic cracks. These cracks usually appear in thick coating areas, but are not limited to those areas.

How to improve the cleanliness of the tank liquid and strengthen the daily maintenance and management of the tank liquid is the most effective shortcut to improve the quality of surface treatment processing, improve work efficiency, and save costs. The method to improve the cleanliness of the tank liquid is tank liquid purification. Tank liquid purification technology includes purification technology for newly prepared tank liquid and purification technology for impurity ions in daily production. Tank liquid purification technology does not only specify the filtration period of tank liquid. The author has summarized the purification technology of bright nickel plating bath based on years of experience in surface treatment work, for your reference.

① The purification technology for the new solution (1) injects 1/3 to 2/3 of pure water into an independent treatment tank, and dissolves the required amount of nickel sulfate and nickel chloride in the tank when the tempera