To reduce the zinc slag, it is necessary to reduce the content of iron in the zinc liquid, that is, to reduce the factors of iron dissolution:
(1) Plating and heat preservation should avoid the peak area of iron dissolution. That is, do not operate at 480-510 °C.
(2) The zinc pot material should be welded with Hot Dip Galvanized Coils containing carbon and low silicon content as much as possible. The high carbon content will accelerate the corrosion of the iron pot by the zinc liquid, and the high silicon content can also promote the corrosion of the iron by the zinc liquid. At present, the 08F high-quality carbon steel plate is mostly used. Its carbon content is 0.087% (0.05% to 0.11%), the silicon content is less than or equal to 0.03%, and elements such as nickel and chromium that can inhibit iron corrosion are contained. Ordinary carbon steel cannot be used. Otherwise, the zinc consumption will be large, and the life of the zinc pot will be short. Using silicon carbide to make a molten zinc tank has also been proposed. Although the iron loss can be solved, the molding process is also a difficult problem.
(3) To scour the slag frequently. First, raise the temperature to the upper limit of the process temperature to separate the zinc slag from the zinc liquid. Then, drop it below the process temperature, so the zinc slag settles at the bottom of the tank and is picked up with a spoon. The plated parts that fall into the zinc solution should also be salvaged in time.
⑷To prevent the iron in the flux from being brought into the zinc bath with the workpiece; reddish-brown iron-containing compounds will be formed when the flux is used for a certain period of time, which should be filtered out regularly. It is better to maintain the pH value of the plating agent at around 5.
⑸ Less than 0.01% of aluminum in the plating solution will accelerate slag formation. An appropriate amount of aluminum not only improves the zinc solution’s fluidity and increases the coating’s brightness but also helps reduce zinc slag and ash. A small amount of aluminum floating in the liquid is beneficial to reducing oxidation and excessively affects the quality of the coating, resulting in spot defects.
⑹ Heating and Heating should be uniform to prevent explosion and local overheating.