Quality Defects and Precautions of Galvanized Sheet

Common quality defects of galvanized sheet

Defect name	Defect performance	Cause
Galvanized peeling	Dezincification	Poor furnace temperature, improper substrate processing, etc.
Not galvanized	Part of the steel plate surface is not galvanized	poor raw materials, poor pre-treatment degreasing, poor furnace temperature
Bad spangle	Uneven spangle size, no spangle	Poor heating in the furnace area and poor cooling control
Zinc scar	Point and granular zinc dross attached to the surface of the steel plate	The scum or bottom dross in the zinc pot adheres to the steel belt
Oxidation	White rust	During storage, it absorbs moisture in the air and oxidizes. 2Zn+O2 → 2ZnO 5ZnO+2CO2+3H2O →2ZnCO3·3Zn(OH)2
Dark Spot	Black dots, blocky spots	Impurity precipitation reacts with moisture and carbon dioxide in the atmosphere, or friction during transportation.
Wave	Wavy edges or middle	Poor raw material or poor working condition of the pull-straightening roller.
Jagged edge	Jagged edges	When the raw material is cold rolled, the edges are uneven and jagged.
Uneven surface	Dent	Pits in the raw material or adhesion of foreign matter on the surface of the roller

Matters needing attention in the transportation and storage of galvanized coils

1.Choose a ventilated place in the house to avoid dew erosion or moisture penetration;
2.Make sure that the packaging paper is not damaged during storage;
3.Shorten the storage time as much as possible and protect its surface before corrosion;
4.If the plate is subjected to abnormal external pressure, the zinc layer will partly fall off;
5.Prevent dirt and oil powder from sticking to the surface, which will affect the galvanizing effect;
6.Skids or support frames should be added under the steel coils, and the number of stacked layers should not exceed two;
7.The rain cloth should be covered during transportation, and it must be cushioned with skids and rubber, and fixed with ropes.