69. What are the factors affecting the growth rate of zinc ash?

Zinc ash is an oxide of zinc formed through oxidation when zinc liquid comes into contact with air. This layer of zinc ash initially forms, isolating the underlying liquid zinc from air and preventing further oxidation. However, in actual production, this isolation cannot be maintained. Scratching the surface exposes fresh zinc liquid to air, causing continuous zinc ash formation.
The growth rate of zinc ash is determined by the following factors: (1) Zinc bath temperature: Higher temperatures accelerate oxidation, resulting in increased zinc ash formation. (2) Zinc bath surface condition: A larger surface area exposed to air (e.g., wider galvanizing pot openings) leads to more ash production. (3) Indoor airflow: Increased ventilation volume from dust extraction systems and cooling fans speeds up air exchange on the zinc bath surface, enhancing oxygen exposure and zinc oxidation, thus increasing ash generation. (4) Zinc composition: Higher purity accelerates oxidation, with ash accumulation. Magnesium content (0.1-1%) in zinc significantly increases oxidation rates compared to pure zinc. To achieve desired galvanizing patterns (especially in thin sheet production), adding antimony to the zinc bath slightly increases ash formation. Conversely, aluminum addition forms an aluminum oxide film on the zinc surface, isolating it from air and reducing ash production.
(5) The drying degree of steel pipe is not enough, when the steel pipe with moisture contact with the aluminum liquid film and zinc liquid on the surface of the zinc liquid, the oxidation speed is accelerated, and the zinc ash increases.