Removal of Organic Impurities in Potassium Salt Zinc Plating Solution for Electric Heating Tube Electroplating

Removal of Organic Impurities in Potassium Salt Zinc Plating Solution for Electric Heating Tube Electroplating

Potassium salt zinc plating has been widely used due to its advantages of environmental protection, energy conservation, and easy operation. However, after a long period of use of the zinc plating solution, a large amount of organic decomposition products will accumulate in the plating solution. During electroplating, black spots will appear on the surface of the zinc plating layer, affecting the surface quality of the passivated workpiece. The traditional method for treating organic decomposition impurities in zinc plating solution is to add hydrogen peroxide. But with the application of new brighteners, there are more and more organic compounds with longer chains that are not easily decomposed. Using hydrogen peroxide for treatment can result in incomplete decomposition of organic matter, shortened plating treatment cycle, and increased treatment costs.

We use the potassium permanganate method to treat organic decomposition impurities in the zinc plating solution. Practice has proven that the treatment is thorough and the effect is good.

1. Plating solution treatment

Take 30mL of plating solution and adjust the pH value of the plating solution to below 3, Heat to 50-60 C, gradually add potassium permanganate, 0.59 times each time. At this point, a large amount of black MnoZ precipitates are found to be generated. During the addition process, it is necessary to continuously stir and add sulfuric acid to keep the pH value below 3. Because potassium permanganate has the strongest oxidation ability under strong acidic conditions. When the solution shows a slight purple red color and can remain unchanged for a few minutes, it indicates that the amount of potassium permanganate added is sufficient. At this time, an additional 1-3 mJ of hydrogen peroxide is added, React with excessive potassium permanganate. Use a sodium hydroxide solution with a concentration of lmol to increase the pH value of the plating solution to 5-6. At this point, there is a large amount of Fe in the plating solution, which will be converted into precipitation. According to re (oH), it can be inferred that when the pH value is above 3.5, the concentration of Fe will decrease to below 10-1 mol/L. At a pH value of 5-6, most heavy metal ions will be converted into precipitates. Add 2 L of zinc powder and stir for 0. sh. Then add 2-3 L of activated carbon and stir for 0. sh. Filter. Excess hydrogen peroxide can be removed under the condition of 50-60 "c and heat preservation of 0.sh, and can be tested with Potassium iodide-starch test paper.

The filtered solution is electrolyzed with a low current resistance of 0. IA/d for 1-2 hours. The content of each component in the plating solution is analyzed, supplemented as needed, and then a brightener is added for trial plating.

We used this treatment method to treat zinc plating solution on the front line of the enterprise site. After treatment, the plating solution is clear and the trial plating quality is good, which has been recognized and praised by the manufacturer.

2 Conclusion

The use of potassium permanganate to treat organic decomposition impurities in potassium salt zinc plating solution has good results, thorough treatment, simple operation, and good feasibility in practice, which can bring certain economic benefits to enterprises.

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