The appearance defect of GI steel coil
(6) Slag inclusion
The galvanizing solution has residues or scum (metallic or non-metallic inclusions). Sometimes these slag inclusions are included in the galvanized layer, making small round spots appear on the surface. Even the original plate cannot be stained with zinc, quickly exposing iron.
(7) Scratches and abrasions.
When the galvanized coil passes through the tension leveler, foreign objects in the leveler cause surface scratches, abrasions, etc.
(8) Chromic acid dirt
To improve the anti-corrosion ability of galvanized steel sheets, a thin passivation layer is formed on the surface of the strip steel, which can be completed by chromic acid treatment, that is, chromatin treatment. However, if the chromic acid treatment is not good and there is residual liquid, the surface of the galvanized sheet will appear yellowish bands or stains to black spots.
