Galvanizing with spots means that zinc spangles will be produced when the zinc layer condenses under normal conditions after galvanizing, while galvanizing without spots requires controlling the lead at a certain level, or undergoing special treatment after the strip steel leaves the zinc pot to obtain galvanized products without spots. Long ago, hot-dip galvanized products always had some zinc spangles on the surface because the lead in the zinc liquid could not be refined very pure, so our traditional concept is that hot-dip galvanizing has zinc spangles. With the development of the automobile industry, if hot-dip galvanized automobile plates need to be painted, zinc spangles will have an impact on the painting. Later, by reducing the lead content in zinc ingots and zinc liquid to dozens of ppm (one millionth), we can produce products with no or very little zinc spangles.
Zinc spangles are a surface morphology of hot-dip pure zinc sheet coils. When the steel strip passes through the zinc pot, the surface is coated with liquid zinc. Then, during the natural solidification of the zinc layer, zinc grains nucleate and grow to form zinc spangles.
The name “zinc spangles” comes from the snowflake-like morphology of complete zinc crystals. The most complete shape of zinc crystals resembles snowflakes or hexagonal stars, so the zinc crystals obtained by condensation on the surface of the strip through the hot-dip process are most likely to be snowflakes or hexagonal star-shaped zinc flowers.