The mastery and control of hot-dip galvanizing operating conditions

(1) pH value During the electroplating process, the pH value gradually rises. Therefore, it is necessary to frequently test and adjust the pH value of the hot-dip galvanizing bath. The pH test paper should be of precision grade, and a wide range of pH test papers ranging from 1 to 14 cannot be used. Use 3. 8-5.4 precision test paper. Due to the use of test papers from different manufacturers, the pH value of the same hot-dip galvanizing tank will have different test results. Two test papers produced by the same company have different test results due to different pH test ranges. This requires us to try our best to buy the same test paper and the same specification test paper to measure the plating solution, in order to minimize the error.

When measuring the pH value of the hot-dip galvanizing bath, if the pH value of the bath is found to change rapidly, it indicates that the concentration of boric acid in the bath is insufficient.

After confirming that the pH value is higher than the normal range, adjust the pH value of the plating solution with dilute hydrochloric acid (mass fraction 20%-30%). When acid is added to the hot-dip galvanizing bath, a white smoke-like phenomenon occurs, that is, the brightener contains benzene. When sodium formate encounters strong acid, it releases water-insoluble benzoic acid. Therefore, when adding hydrochloric acid, pay attention to stirring the plating solution, and measure the pH value while stirring when adding acid. After reaching the standard range, stop adding acid solution.

When adjusting the pH value, only use hydrochloric acid instead of sulfuric acid or other acids, otherwise it will cause trouble.

If the pH value is too low due to the mistaken addition of too much hydrochloric acid, use dilute lye (10%-20% sodium hydroxide aqueous solution) to slowly adjust it back. But stir vigorously. Otherwise, zinc hydroxide precipitates will form.

(2) Temperature The temperature of the hot-dip galvanizing tank is mainly closely related to the season and the environment. However, during the electroplating process, the hot-dip galvanizing bath will naturally rise. Especially when the content of the components in the hot-dip galvanizing bath is low (especially the two components of KC1 and ZnCl2) and the anode area is small, the liquid temperature rises faster.

In the cold winter in the north, the temperature of the hot-dip galvanizing tank is only 4 degrees, which is not suitable for electroplating. Only when the temperature of the plating solution rises above 101 through external heating, can normal production be realized. In summer, the bathing temperature in the south can reach 501 degrees. Although a brightener synthesized by a high-temperature carrier is used, the dispersion ability of the plating solution is poor, and the brightness in the low current area is still not ideal. Manual cooling measures must be taken to keep the bath temperature at 4 (n): The following are the necessary conditions for obtaining high-quality coatings. The cooling method is to install a heat exchange tube (titanium tube, quartz glass tube or lead tube) on the inner wall of the plating tank, and refrigerant or tap water can be used in the tube to reduce the temperature of the hot-dip galvanizing tank.