The sinking roller scratch is the mutual movement between the strip and the sinking roller, the speed of the two is inconsistent, the relative sliding occurs, and the surface of the strip is scratched by the surface of the sinking roller. Specifically, the strip is hot-dip galvanized from the nose of the annealing furnace into the zinc pot, and is turned to the zinc pot through the sinking roller. Since the sinking roller is in a special position in the zinc liquid, it is not suitable for the motor to be driven.