How do aluminum-containing and aluminum-free zinc baths differ in their corrosion effects on iron?

When steel pipes are immersed in zinc for a very short period, the corrosion rate in aluminum-free galvanizing pots is approximately 7-9 times faster than that in aluminum-containing galvanizing pots. However, when the immersion time exceeds 8 minutes, the corrosion rate in aluminum-containing galvanizing pots becomes higher than that in aluminum-free ones. The former is advantageous for rapid zinc immersion to increase production, while the latter has adverse effects on galvanizing pots. Therefore, in actual production with aluminum-added galvanizing pots, it is observed that the pits corroded on the steel plates of the galvanizing pots at the zinc bath surface are relatively deep.