Most of the sinking rolls are passive rolls, which rely on the friction between the strip surface and the surface of the sinking roll to move the sinking rolls at the same speed as the strip; but sometimes due to mechanical equipment, production process control, use of sunken rolls, etc. The influence of the factors causes the transmission friction between the strip and the sinking roller to be insufficient, and the strip and the sinking roller slide relative to each other, thus causing surface defects of the sinking roller of the hot-dip galvanized product.