1995 Volume 81 Issue 6 Pages 643-648
The liquid film flow on a strip steadily moving upward from a coating liquid bath in the gas wiping process for continuous hot-dip coating was analytically investigated assuming that the flow was time-independent and laminar and the surface tension was negligible. The coating thickness profile of the liquid film can be estimated by solving the equation of motion under the boundary conditions that both the impinging pressure and the shear stress of the gas wiping jet act on the liquid film surface. The analytical results of the coating thickness profiles agree well with the experimental results measured by the needle electrode method using glycerine-water solution. The analytical results were also compared with data obtained in a commercial hot-dip galvanizing line. It is confirmed that the effects of the line speed, the nozzle pressure, the nozzle-to-strip distance and the nozzle slit gap on the zinc coating weight can be explained well by the analysis and that the coating weight can be estimated within ±20% accuracy.