The main factors that affect the thickness of the hot-dip galvanized coating are: the base metal composition, the surface roughness of the steel, the content and distribution of active elements silicon and phosphorus in the steel, the internal stress of the steel, the dimensions of the workpiece, and the hot-dip galvanizing process. The current world and my country hot-dip galvanizing specifications distinguish sections based on the thickness of the steel. The average thickness and partial thickness of the zinc coating should reach the corresponding thickness to determine the anti-corrosion function of the zinc coating. For workpieces with different steel thicknesses, the time required to reach thermal equilibrium and zinc-iron AC equilibrium is different, and the thickness of the formed coating is also different. The average thickness of the Shandong hot-dip galvanized coating in the specification is based on the industrial production experience value of the above-mentioned galvanizing mechanism, and part of the thickness is an empirical value that takes into account the unevenness of the zinc coating thickness distribution and the requirements for the corrosion resistance of the coating. Therefore, the requirements for the thickness of the zinc coating are slightly different in the ISO standard, the American ASTM standard, the Japanese JIS standard and the Chinese standard.

Now the development of hot-dip galvanizing technology has been improved, and new requirements have been placed on production technology.

(1) Unit development towards high production capacity

The hot-dip galvanizing units built since the 1990s are developing towards high production capacity. Shandong has more than 60 hot-dip galvanizing units with a global production capacity of more than 300,000 t/a. The total production capacity exceeds 28 million t/a. a.

(2) Unit specialization

The production of galvanized sheets for cars and building materials is produced by different types of units. The unit technology, individual equipment and furnace selection are more reasonable, which makes the investment effect significant and reduces product costs.

(3) Emphasize the cleanliness of the substrate surface

In recent years, the steel plate galvanizing unit for cars built in recent years basically uses the alkaline solution electrolytic cleaning and the all-radiant tube heating furnace of the American Steel Union process to increase the economy, and even sets the cleaning section before and after the looper equipment. In order to reduce investment, building material-type galvanizing lines mostly use the improved Sendzimir process, but the line is mostly equipped with a cleaning section to make the substrate surface cleaner and product quality better.