What is it?
This defect appears as a diagonal line, approximately 1-4 inches wide across the width of a galvanized coil. The defect can also be in a zig-zag pattern depending on the severity of air knife slit clogging. It can also be known as knife swipe. This defect is usually caused when liquid zinc gets trapped in the air knives along the galvanizing line, resulting in spooling or build-up. The operators must clear the knives by passing a shim through the knife gap, which interferes with air flow as it passes through.