What is it?

This galvanized defect usually looks like there are half-moon marks on the steel. It can also be known as galvanize snakes or air knife cleanout. It is usually caused when operators manually insert a cleaning tool across the air knife, located above the galvanizing bath, to dislodge debris caught in the slit. The movement of the tool in and out of the slit creates the half moon look of the defect. The defect is usually isolated in the coil and near a coil’s end. Plugged air knives create coating lines in the zinc surface that are unsuitable for painting.

Die Cleanout Mark (Half moon)

Die Cleanout Mark (Half moon)