When the clean iron or steel component is dipped into the molten zinc (commonly at 450°C) a series of zinc-iron alloy layers are formed by a metallurgical reaction between the iron and zinc. The rate of reaction between steel and zinc is normally parabolic with time and so the initial rate of reaction is very rapid and considerable agitation can be seen in the zinc bath. The main thickness of coating is formed during this period. Then the reaction slows and the coating thickness is not increased significantly - even if the article is in the bath for a longer period of time. A typical immersion time is about 4 or 5 minutes but it can be longer for heavy articles that have high thermal inertia or where the zinc has to penetrate internal spaces. On withdrawal from the galvanizing bath a layer of molten zinc will be taken out on top of the alloy layer. Often this cools to exhibit the bright shiny appearance associated with galvanized products.

  Conditions in the galvanizing plant such as temperature, humidity and air quality do not affect the quality of the galvanized coating. By contrast, these are critically important for good quality painting.