A control for a sheet metal processing line with a descaler includes sensors that adjust the spray blast pattern produced by impellers and the sheet advancement rate during descaling. The control may position a nozzle of the impeller so when a surface condition of the edge of the sheet is more favorable than that of the center of the sheet, the impeller spray concentration moves toward the center, and when a surface condition of the center of the sheet is more favorable than that of a respective edge of the sheet, the impeller spray concentration moves away from the center of the sheet. The control may raise the sheet advancement rate when the surface condition of the center of the sheet is more favorable than a standard, and lower the sheet advancement rate when a surface condition of the center of the sheet is less favorable than a standard.